Here is the honest verdict on the build vs buy software question: most of the time, you should buy. Off-the-shelf SaaS covers the majority of business operations well enough, and the real cost of custom software is almost always higher than founders expect. But there is a specific set of conditions where commissioning bespoke software is not just defensible, it is the sharper move. This piece gives you a framework for telling the difference, built from actually shipping products and advising lean teams, not from vendor marketing.
Why Most Build vs Buy Advice Is Useless
The majority of content on this topic is written by SaaS vendors (biased toward buy) or software agencies (biased toward build). Neither is giving you the full picture. The vendor wants your subscription. The agency wants your project budget. What you actually need is a way to pressure-test the decision against your specific constraints: your team size, your runway, your competitive position, and where the software sits in your business model.
The second problem is abstraction. Most frameworks give you a vague checklist of considerations without telling you how to weight them. This one does not do that. I will tell you what actually matters and in what order.
The Core Question: Is the Software Your Product, or Does It Support Your Product?
This is the most important filter in the entire decision. If the software is the thing you are selling, or if it creates a capability that competitors cannot easily replicate, building is almost always the right call. If the software is infrastructure that enables your real work, buying is almost always right. A bespoke CRM for an agency is almost never worth it. A bespoke matching algorithm for a marketplace that lives or dies by match quality might be the entire business.
Ask yourself: if a competitor had access to the same SaaS tool tomorrow, would it close the gap between you? If yes, the tool is not a competitive asset. It is a commodity. You should buy it and spend your energy elsewhere.
Build vs Buy: The Decision Framework
Work through these four questions in order. Each one can settle the decision before you reach the next.
- Does the off-the-shelf option cover 80% of your core workflow? If yes, start there. Gaps in the remaining 20% are almost always cheaper to work around or automate lightly than to build from scratch. The exception is when that 20% is load-bearing: when it is the thing customers actually pay for.
- Have you already hit the ceiling of the SaaS tools in this category? Switching from SaaS to custom because you 'might outgrow it' is a trap. Build when you have demonstrably outgrown it, not when you're worried you might.
- Can you maintain what you build? Custom software creates an ongoing obligation. You need someone who can update it, debug it, and extend it. If you are a solo founder with no technical resource, the total cost of ownership for a bespoke build is often invisible until it bites you.
- Is the process the software would automate actually stable? If your workflow is still changing week to week, you are not ready to build. You will encode today's assumptions into code and then spend money unpicking them next quarter.
Custom Software vs Off the Shelf: A Direct Comparison
| Factor | Buy (SaaS / Off the Shelf) | Build (Custom Software) |
|---|---|---|
| Upfront cost | Low to moderate subscription cost | High: design, development, testing, launch |
| Time to value | Days to weeks | Weeks to months, often longer |
| Ongoing cost | Predictable monthly/annual fee | Maintenance, hosting, iteration cycles |
| Customisation ceiling | Limited to vendor's roadmap | Unlimited, constrained only by budget and time |
| Competitive differentiation | None (competitors can use the same tool) | High, if the software encodes a proprietary process |
| Maintenance burden | Carried by the vendor | Carried by you or your technical team |
| Best fit | Commodity workflows: comms, finance, HR, CRM basics | Core product logic, proprietary workflows, unique data models |
| Risk profile | Low operational risk, vendor lock-in risk | Higher execution risk, lower long-term dependency risk |
Where Founders Go Wrong on Both Sides
The most common mistake on the buy side is stitching together too many SaaS tools to compensate for not building the right thing. I have seen lean teams running eight or nine subscriptions that together approximate one piece of software they needed. The integration overhead, the data fragmentation, and the monthly cost often exceed what a focused build would have cost over two years.
The most common mistake on the build side is commissioning custom software before the process it is meant to support has been validated. You end up building a very polished solution to a problem that turns out not to be the real problem. Always validate the workflow manually or with lightweight tooling first. Build the custom solution when you know exactly what you are encoding.
Watch out for the 'we'll build it our way' instinct in founders who have had bad experiences with rigid SaaS tools. The frustration is valid, but it is not a sufficient reason to build. Frustration with a tool means you need a better tool, not necessarily a custom one.
The Middle Path: When a Hybrid Makes More Sense
The binary framing of build vs buy misses a third option that lean teams underuse: a thin custom layer on top of existing infrastructure. Buy the commodity parts (authentication, payments, notifications, document storage) and build only the core logic that is genuinely yours. This is how most of the products I have shipped are structured. It compresses timelines significantly and keeps maintenance scope contained. You are not building a platform; you are building the specific thing that only your business needs.
The Real Cost of Custom Software
Founders consistently undercount the cost of custom builds. The development quote is the starting point, not the total. Factor in: product design and scoping, QA and testing, hosting and infrastructure, ongoing bug fixes, iteration as your needs evolve, and the cost of your own time spent managing the process. For a lean UK-based team with no in-house technical lead, those invisible costs can double or triple the initial figure. That does not make building wrong. It means you should go in clear-eyed about what you are committing to.
When to Build: The Short List
After filtering through the framework above, these are the situations where commissioning custom software consistently makes sense:
- The software encodes a proprietary process or data model that is central to your competitive position
- You have validated the workflow thoroughly and it is stable enough to encode
- You have a technical resource (in-house or a trusted partner) who can own the build and maintain it
- The cumulative cost of SaaS subscriptions and integration workarounds has crossed the threshold of a focused build
- Off-the-shelf options in the category are genuinely weak or non-existent for your specific use case
- You need control over your data that SaaS vendors cannot offer (relevant in regulated sectors or where data is the asset)
A Note on SaaS vs Custom Development Over Time
The right answer at year one is rarely the right answer at year three. Many businesses should start with SaaS and migrate to custom tooling as the process matures and the economics tip. The mistake is treating the decision as permanent. Build a review into your roadmap: every time a SaaS tool becomes a meaningful constraint on growth, revisit the question with the framework above. Do not build out of frustration; build out of clarity.
How do I calculate whether it's cheaper to build or buy software?
Add up your total SaaS spend in the category over a two to three year horizon, including integration tools and any workaround tooling you layer on top. Compare that to an honest estimate of the custom build cost, including design, development, testing, hosting, and at least one year of maintenance. If the SaaS total exceeds the build total and the process is stable, the economics favour building. If not, they favour buying. Most founders find the SaaS option is cheaper than they expected and the build option is more expensive.
What are the biggest risks of commissioning custom software?
The three biggest risks are: building before the process is validated (you encode the wrong assumptions), underestimating maintenance cost (custom software needs someone to own it long-term), and choosing the wrong technical partner (a slow or misaligned development team turns a six-month project into an eighteen-month one). Mitigate all three by validating the workflow first, budgeting explicitly for maintenance, and working with a partner who has shipped comparable things before.
Can a non-technical founder commission custom software successfully?
Yes, but it requires more rigour, not less. A non-technical founder should invest time in scoping the requirement precisely before any code is written, work with a partner who communicates clearly in plain terms, and build in regular review points rather than handing over a brief and waiting. The failure mode for non-technical founders is not that they cannot commission software; it is that they under-specify the brief and over-trust the process.
Is off-the-shelf software always faster to implement than custom?
Usually yes, but not always. Complex SaaS implementations with heavy configuration, data migration, team training, and integration work can take weeks or months. A focused custom build with a clear scope can sometimes deliver a working tool faster than configuring a sprawling enterprise SaaS platform. The gap closes significantly when the SaaS tool is a poor fit and requires extensive workarounds to function.
When does the build vs buy decision come up most often for lean teams?
Most commonly at three inflection points: when a SaaS tool raises its prices significantly, when a core workflow has grown too complex for the tools currently supporting it, and when a founder realises a proprietary process could be a product in its own right. The third scenario is the most strategically interesting and the one most worth exploring carefully.