Build vs buy for small businesses, settled by math

"Should we build it or buy it?" is one of the most consequential questions a small business faces — and it's almost always answered by preference rather than math.

Founders who love tinkering tend to build. Founders who've been burned by engineering projects tend to buy. Neither instinct produces the best decision on its own. Here's the framework we use with clients to settle it on the numbers.

The four-year question

Most build-vs-buy debates happen in the wrong time horizon. People compare this month's SaaS invoice to a one-time build cost and declare a winner.

Look at four-year total cost of ownership instead. Over four years, here's what you're actually comparing:

Buy: monthly subscription × 48 months + implementation + per-user creep as you grow + the inevitable annual price increase. Add integration costs if the platform doesn't natively talk to your other systems.

Build: design + build + deployment + ongoing maintenance × 48 months + hosting + the feature requests you didn't anticipate in v1.

The surprise is usually that buy is more expensive at scale than founders expect — especially once per-user pricing kicks in — and build has more ongoing maintenance than engineers like to admit.

The three questions that decide it

Once you have honest four-year numbers, three questions determine the answer:

1. Is this core to how your business is differentiated?

If the workflow is something your competitors do too, and the market has produced good software for it (CRM, accounting, email, scheduling), buy is almost always right. You will never out-build a well-funded SaaS company on their home turf, and you don't need to.

If the workflow is specific to how you deliver value — and your competitors would want to copy it — that's worth considering building. Your unique process is hard to compress into a generic tool.

2. Does an off-the-shelf product fit 80%+ of your needs out of the box?

80% is the threshold. Below it, you'll spend your life in configuration hell, hacking around the 20% that doesn't fit and paying professional services to keep it glued together. Above it, buy and move on.

Ignore demo-happy checklists. Fit means fit on your top three workflows, not the vendor's feature matrix.

3. Do you have the ability to maintain what you build?

Custom software is a pet, not a one-time project. It needs attention as your business changes, as vendors update their APIs, as security patches come out. If you don't have a technical owner — internal or trusted external — buy is right regardless of the other answers.

The hybrid answer almost nobody picks

For most SMB scenarios, the right answer is actually a third one: buy the platform, automate the integration.

Use proven SaaS for the commoditized parts (CRM, accounting, email, project management). Then build small, focused automation and integration layers that connect them in the way your business actually runs. That's where the differentiated leverage lives — in the glue, not the apps.

This is the work we do most often with clients. And it's the shape of answer that most buy-vs-build conversations miss.

One more thing

Whatever you decide, document the decision. Six months from now, someone will propose ripping out what you chose and going the other direction. Having a written record of the four-year math and the three questions makes the next conversation 10× shorter.

The decision itself matters. Being able to defend it — and revisit it — matters almost as much.