Build, buy or partner

Every capability your business needs can be done by your own people and systems (first party), bought as a product or handed to an outside service or partner (third party). In short, build what makes customers choose you, buy what is standard and hire a service when the work needs skills or scale you cannot keep busy all year. The steps below cover the decision, with a five-year total cost of ownership comparison, the hidden costs that usually tip it and a weighted decision matrix you can reuse.

Disclosure

Lumina ERP is a consultancy, so "hire a partner" is one of the options we sell. We have tried to keep this guide neutral, and in many of the cases it describes the right answer is to build or buy without us or anyone like us.

The options at a glance

Option	What it means	Best when	Typical cost shape	Main risk
Build (first party)	Your staff write it, run it or do it	The work is core to how you win, or nobody sells a good fit	High internal time, low fees	Key-person dependence, slow delivery
Buy a product	License or subscribe to software and run it yourself	The need is common and products are mature	One-time setup, recurring fees, moderate internal time	Fit gaps, price increases, vendor failure
Hire a service or partner	An outside business does the work for you	Work is specialized, seasonal or needs scale	Recurring fees, low internal time	Less control, dependence, quality drift
Hybrid	Buy a product and pay someone to run or extend it	You want a product but lack the skills to run it	Fees on two contracts	Two parties to coordinate, finger-pointing

Before you start

• A one-paragraph description of the job to be done, in business terms, not a product name.
• A rough volume: transactions, users, sites, hours per month.
• A named business owner who will live with the result.
• A realistic loaded hourly rate for the internal staff involved (see step 4).

Steps

1. Describe the job, not the solution. "Capture 3,000 supplier invoices a month into AP with three-way match" is a job. "Buy an AP automation tool" is a solution. Writing the job first keeps all three options open.

2. Decide whether it is core or context. Geoffrey Moore's core versus context idea (from his book Dealing with Darwin) is the most useful single filter. Core work differentiates you: customers choose you because of it. Context work must be done well but earns no preference when it is. For most distributors, pricing strategy, local inventory availability and technical sales are core. Payroll, tax calculation and invoice capture are context. Build or tightly control core work. Buy or outsource context work.

3. Score the options against the criteria. Use the criteria table below. Drop any option that fails a must-have outright.

4. Compare five-year total cost of ownership. Include internal time at a loaded rate as well as invoices. The worked example below shows how.

5. List the hidden costs and risks. Upgrades, key people, switching and data exit. They rarely appear on a quote.

6. Run the decision matrix. Weight the criteria before you score, so the weights cannot be bent to fit a favorite.

7. Pilot or reference check. For buy and partner options, talk to two customers of your size. For build, prototype the hardest part first.

8. Record the decision and a review date. Write down why you chose, what would change your mind and when you will look again (usually at contract renewal or the next ERP upgrade).

Core or context: examples for a distributor

Capability	Usually	Why	Exception
Customer-specific pricing logic	Core, build or configure in the ERP	It is how you compete on margin	Almost never. Keep control
Sales tax calculation	Context, buy	Rates and rules change constantly across thousands of jurisdictions	Single-state business with few exempt customers
EDI with large customers	Context, buy a service	Standards work and partner testing need specialists	Very high volume with in-house X12 skills
Warehouse operations	Core for most	Speed and accuracy are what customers notice	A 3PL is better for overflow, a new region or e-commerce spikes
AP invoice capture	Context, buy	Common problem, mature products	Very low volume where manual entry is cheaper
Payroll	Context, buy or outsource	Compliance-heavy, no competitive value	Rarely
Custom reporting	Mixed	Some reports are how you manage the business	Build the few that matter, buy a reporting tool for the rest
IT infrastructure	Context, partner or cloud	Hard to staff around the clock at small scale	Large IT team with spare capacity

Criteria to weigh

Criterion	What to ask	Favors build	Favors buy	Favors partner
Fit to your process	How much of the job does it do without change?	Unusual process	Standard process	Standard process, specialist skill
Time to value	When does it start paying back?	Rarely fast	Weeks to months	Often fastest
Five-year cost	Total including internal time	Low fees, high time	Balanced	High fees, low time
Control	Can you change it when you need to?	Full	Limited to configuration	Limited to the contract
Skills required	Do you have them, and will you keep them?	You have and will keep them	Admin skills only	You do not have them
Upgrade path	What happens at the next ERP release?	You retest	Vendor certifies	Partner handles, at a price
Risk and resilience	What if the key person or vendor leaves?	Key-person risk	Vendor risk	Vendor and quality risk
Data and security	Where does your data go?	Stays with you	To the vendor	To the provider and its providers
Exit	How hard is it to stop?	Easy to stop, hard to replace	Data export and replacement	Transition and knowledge transfer

Total cost of ownership

Total cost of ownership (TCO) is everything you spend to get and keep a capability over its life, not only what you pay the vendor. The GAO Cost Estimating and Assessment Guide (GAO-20-195G, March 2020, retrieved 2026-09-28) makes the same point for government programs, asking for an estimate of the full life cycle rather than the purchase price.

Total cost of ownership

One-time cost + sum of annual fees over the years + internal hours per year × loaded hourly rate × years

Where:

• One-time cost is implementation, setup, data migration, training and any hardware.
• Annual fees are subscription, license maintenance, hosting or service fees, increased each year by the escalator in the contract.
• Internal hours are the time your own staff spend running, supporting, testing and managing the capability.
• Loaded hourly rate is what an hour of that staff time costs you, not what the person is paid.

Getting the loaded rate right

A loaded rate adds benefits, payroll taxes and overhead to wages. The BLS Employer Costs for Employee Compensation release for June 2026 (retrieved 2026-09-28) puts private industry compensation at $46.89 per hour worked, of which wages and salaries were $32.82 (70.0%) and benefits $14.07 (30.0%). So benefits alone add about 43% on top of wages, before office space, equipment, software and management time. Many finance teams use a rule of thumb of 1.3 to 1.5 times wages for benefits plus overhead. It holds for salaried office staff and understates the cost of specialists you would have to hire.

Worked example: AP invoice capture

These numbers are invented and round. A mid-sized industrial distributor processes about 3,000 supplier invoices a month and compares three ways to automate capture over five years. Internal time is costed at a loaded $85 per hour for all three.

Input	Build (own scripts and OCR)	Buy (AP automation product)	Partner (outsourced AP service)
One-time cost	$60,000	$25,000	$5,000
Year 1 annual fees	$3,000 (hosting)	$12,000 (subscription)	$30,000 (per-invoice fees)
Annual increase	3%	5%	3%
Internal hours per year	400	120	60

Year-by-year fees for the buy option, with the 5% escalator:

Year	Subscription
1	$12,000.00
2	$12,600.00
3	$13,230.00
4	$13,891.50
5	$14,586.08
Total	$66,307.58

For the buy option, five-year TCO is $25,000 one-time plus $66,307.58 in subscription fees, which is $91,307.58 paid to the vendor, plus 120 hours × $85 × 5 years = $51,000 of internal staff time. The total is $142,307.58, an average of $28,461.52 a year, and internal time is 35.8% of the total.

Result over 5 years	Build	Buy	Partner
One-time cost	$60,000.00	$25,000.00	$5,000.00
Annual fees, all years	$15,927.41	$66,307.58	$159,274.07
Internal staff time	$170,000.00	$51,000.00	$25,500.00
Total cost of ownership	$245,927.41	$142,307.58	$189,774.07
Average per year	$49,185.48	$28,461.52	$37,954.81
Internal time as share of total	69.1%	35.8%	13.4%

Two lessons from the invented numbers. First, the build option looks cheapest on invoices (under $76,000 of cash to outsiders) and is the most expensive in total, because 400 hours a year of skilled staff time is real money. Second, even the buy option carries more than a third of its cost as internal time, which never appears on a vendor quote.

Try your own numbers. The calculator opens with the buy option from this example.

Calculator

Total cost of ownership

One-time cost (setup, implementation, data migration) ($)Annual fees in year one (subscription, support, maintenance) ($)Annual fee increase (%)Internal staff hours per yearLoaded hourly cost of that staff ($)Years to compare

Internal hours are the cost most often left out. Count administration, vendor meetings, testing upgrades and fixing the integration, not only the project.

Hidden costs that change the answer

Hidden cost	Hits hardest	How to estimate
Internal time to run it	Build, and buy with heavy admin	Ask the people who will do it for hours per week, then multiply by 52
Upgrades and retesting	Build and custom integrations	Hours to retest at each ERP release, times releases in five years
Key-person risk	Build	Cost to hire and train a replacement, times the chance they leave in five years
Price escalators	Buy and partner	Read the renewal clause. A 7% escalator doubles the fee in about 10 years
Switching and exit	Buy and partner	Data export, replacement setup, parallel running, staff retraining
Vendor management	Buy and partner	Hours a year for reviews, invoices, disputes and renewals
Integration upkeep	All three	Connectors break when either side changes
Opportunity cost	Build	What your best people are not doing while they build this
Quality drift	Partner	Error rates and rework once the provider's A team moves on

Watch the escalator

Check whether the annual increase is capped, tied to an index or at the vendor's discretion. An uncapped escalator makes every five-year TCO comparison a guess. Price protection belongs in the contract, not in a sales email.

The decision matrix

Weight each criterion before scoring, so the weights total 100. Score each option from 1 (poor) to 5 (strong) on each criterion. Multiply and add. The invented scores below are for the AP example.

Criterion	Weight	Build	Buy	Partner
Fit to process	30	5	4	3
Five-year cost	25	2	4	3
Risk and resilience	20	2	4	3
Time to value	15	1	4	5
Control	10	5	3	2
Weighted score (out of 5)	100	3.05	3.90	3.20

Weighted score

Sum of (weight × score) ÷ 100

For the buy option: (30 × 4 + 25 × 4 + 20 × 4 + 15 × 4 + 10 × 3) ÷ 100 = 390 ÷ 100 = 3.90. The matrix supports the TCO result here. When the two disagree, look hard at the weights. If control carries 10% but everyone in the room is arguing about control, the weights are wrong.

Questions to ask

For a build:

• Who will maintain this in three years, and what if that person leaves?
• How many hours will each ERP upgrade cost us to retest it?
• Is this core, or do we enjoy building it?

For a product:

• How many customers of our size and ERP run it, and can we talk to two?
• Which ERP versions is it certified on, and how quickly after a new release?
• What is the renewal escalator, and is it capped?
• How do we export all our data, in what format and at what cost?

For a service or partner:

• Who exactly will do the work, and what happens when they leave?
• What service levels are in the contract, and what are the remedies?
• Which other businesses (fourth parties) will touch our data?
• What does transition back to us, or to another provider, look like?

Red flags

• A build case that counts no internal hours.
• A buy case that counts only year-one subscription.
• A partner quote with no service levels or exit terms.
• "We will customize it to fit" as the answer to a core fit gap in a product.
• A decision that depends entirely on one enthusiastic employee.
• Weights set after the scores are known.

Next steps

• Write the job in one paragraph. Business outcome and volume, no product names.
• Label it core or context. If you cannot agree, it is probably context.
• Agree the loaded rate with finance. One rate for the comparison, stated on the page.
• Build a five-year TCO for each option. Use the calculator and keep the inputs.
• Weight, then score. Weights signed off before anyone scores.
• Record the decision and a review date. Tie the review to renewal or the next ERP upgrade.

Once you have decided to buy or partner, choosing a vendor covers the selection, and contracts, SLAs and data rights covers what to sign. For ERP extensions specifically, see ERP add-ons and ISVs.