Build, Buy or Rent: How to Decide on Your Own Numbers
By Road map ROI, from Cookie Tech, which builds custom software · Published Jun 3, 2026 · Last updated Nov 3, 2026
What changed: Rewritten in plain words, with the same example run again with your own hours and a worst case.
The price tag leaves out part of the cost. Put all of it on one line.
Costs · A few min (est.)
●●●
Total = once + monthly × months + yearly × years + your hours × your rate
- Inputs
- What you pay once · What you pay monthly and yearly · Your own hours · Years
- Output
- One total per option, and what could change it
- When to use
- When you are choosing between a subscription, a ready-made product and a custom build.
- Replaces
- Comparing price tags, or comparing only two of the options.
You need software for your business. You can rent it as a subscription, buy something ready-made, pay someone to build it, or build it yourself. The right answer depends on your numbers, and it can change once you count your own time. This guide runs one example three ways, then points you to the calculator and the guide for each step.
Start with the total
For each option, add what you pay once, what you pay every month and what you pay every year, over the same number of years. If one option is counted over 3 years and another over 5, the comparison tells you nothing.
The example: booking for a clinic
A 15-person clinic needs online booking for 5 years. All the figures here are invented for the example. On cash alone, buying and renting tie, and paying someone costs $30,000 more.
| Option | Pay once | Each year | Cash over 5 years |
|---|---|---|---|
| Pay someone to build it | $90,000 | $18,000 | $180,000 |
| Buy it ready-made | $40,000 | $22,000 | $150,000 |
| Rent a subscription | $0 | $30,000 | $150,000 |
Now add your own hours
Someone has to brief the builder, set the tool up and keep it running. Here that time is valued at $50 an hour, also invented. The tie is gone: renting is now $4,250 cheaper than buying. That is under 3% of the total, so our calculator would call it too close to call. Paying someone is now $47,250 more than renting.
| Option | Your hours | Your time | Total over 5 years |
|---|---|---|---|
| Pay someone to build it | 120 to set up, then 6 a month | $24,000 | $204,000 |
| Buy it ready-made | 40 to set up, then 3 a month | $11,000 | $161,000 |
| Rent a subscription | 15 to set up, then 2 a month | $6,750 | $156,750 |
Then ask what could go wrong
Two things move these totals most: prices rise and builds go over budget. Say the subscription rises 10% a year while the license fee stays flat (our assumption). Renting now totals $189,903, and buying wins by $28,903. Say the build runs 50% over (also our assumption). Paying someone now totals $249,000. Upkeep is the other cost people leave out, so if you build, price it as a yearly line and try 15%, 25% and 40% of the build cost (our assumption, not a measured rate). Build estimates also tend to come in too low, as the studies linked below show. The worst case in our build, buy or rent calculator uses its own assumptions, so its numbers will differ from these: it also raises a ready-made product's yearly fee by 10% a year and sets a builder's upkeep at 40% of the quote a year.
When the numbers are close, decide on fit
If two options land close together, stop adding decimals. Ask who owns your data, what happens if the vendor closes or doubles its price, and whether this tool is what sets your business apart. Our rule of thumb, not a study: only build if it clearly beats the next option, because the extra margin has to pay for the risk that the build goes wrong.
Each step in more detail
These guides and calculators go deeper on each part of the sum.
For product people: the same example in today's money
A dollar you pay in year 5 costs you less than a dollar today, so finance discounts future payments to today (net present value, or NPV). Discounted at 10% over 5 years, the cash figures above become about $158,000 to pay someone, $123,000 to buy and $114,000 to rent. Discounting favors paying later, which is why renting pulls ahead here. The calculator's Expert view shows this at your own rate.
Sources: Flyvbjerg and Budzier, 2011 (1,471 IT projects); Buehler, Griffin and Ross, 1994 (planning fallacy). Other figures on this page are illustrative or our assumption.