Revenue charts tell you what a business earned, but the codebase tells you what it will cost to keep. A SaaS product can look profitable while running on outdated frameworks, undocumented code, and a single developer who holds all the knowledge. Buyers who skip the technical check often discover the real price of the business only after they own it.

Start by asking the seller for a simple architecture overview in plain language. What language and framework does the product use, where is it hosted, what database stores customer data, and which third-party services does it depend on? A seller who cannot answer these basics, or who refuses to, is already showing you a risk.

Next, ask how old the core dependencies are and when they were last updated. Software libraries that have not been updated in years can carry security holes and may break when a hosting provider forces an upgrade. You do not need to judge each library yourself; you need to see whether updates happen regularly or have been ignored.

Documentation is a strong signal of quality. Ask whether there is a written guide for setting up the product, deploying changes, and handling common failures. A business with good documentation can be handed to a new developer in days. A business with none may take months of detective work before anyone can safely change anything.

Find out who can actually change the code today. If only the founder can deploy, fix bugs, or restart a failed service, you are buying a key-person dependency along with the product. Ask whether an outside developer has ever worked on the code, and whether the seller will introduce you to them before closing.

Automated tests are another telling clue. Ask what share of the code is covered by tests and whether tests run automatically before each release. A tested codebase lets you change things with confidence. An untested one means every fix risks breaking something else, and you will pay for that caution in developer hours.

Security basics deserve direct questions, even from non-technical buyers. Ask how passwords are stored, how customer data is backed up, when the last backup was restored as a test, and whether there has ever been a breach. Vague answers here are a reason to slow down, not a detail to skip.

Look at the monthly infrastructure bill and what it includes. Hosting, databases, email delivery, monitoring, and AI or payment services can add up quietly. A business that reports high profit but hides a large infrastructure cost in the founder's personal accounts is less profitable than it appears.

Check the third-party services the product cannot live without. A payment provider, an email service, a mapping API, or an AI model provider can each change prices, close accounts, or discontinue features. List every dependency, note which ones are hard to replace, and ask what would happen if each one disappeared tomorrow.

If the deal is large enough, hire an independent developer for a short code review before you sign. A few hours of expert time can reveal dead code, security gaps, and a realistic estimate for the fixes you will need. For deals above a few thousand dollars, this is some of the cheapest insurance you can buy.

Ask the reviewer for three things in writing: the biggest risks, the rough cost to fix each one, and whether the codebase is worth keeping or rebuilding. That short report gives you negotiating power, because a seller who knows you understand the technical cost is far less likely to hold out for a price the code cannot support.

Use what you learn to shape the deal, not just to decide yes or no. Technical problems can justify a lower price, a holdback for repairs, or a longer transition period with the seller. Walking away is also a valid outcome, and it is far cheaper than buying a rebuild you did not budget for.

The code is part of the business, not a detail beneath it. Treat the technical audit with the same seriousness as the financial audit, and you will avoid the most expensive surprise in micro-acquisitions: a profitable-looking product that costs more to keep alive than it earns.