Turn a SaaS or app idea into a first working version (UK)
Most ideas stall between the notes app and the first line of code. This guide walks through the steps we take founders through: proving the idea, cutting it to one job, choosing web or mobile, budgeting honestly, and the one-page brief that makes the first call with any studio useful.
To turn a SaaS or app idea into a first working version, write down the one job it must do for one kind of customer, check that those customers want it, then build only that job with real sign-in and real payments, and put it in front of real users. Everything else waits for version two. From a UK studio like ours, a first version of a SaaS platform with logins, subscription billing and an admin panel typically costs £25,000 to £60,000 and takes 10 to 14 weeks, while a landing-page test of the idea takes 2 to 3 weeks and can cost as little as a few thousand pounds.
- Write the idea as one job for one customer, in a sentence.
- Test demand first with conversations and a one-page site before paying for a build.
- Cut version one to that job, plus sign-in, payments and the admin view you need to run it.
- Choose web first unless the job happens away from a desk.
- Budget for running costs too, not only the build.
- Bring a one-page brief to the first call with any studio.
How do I turn a SaaS idea into a first working version?
Turning a SaaS idea into a first working version takes six steps: describe the one job it does for one kind of customer, test that people want it, decide what version one leaves out, pick web or mobile, agree a fixed scope and price with whoever builds it, then launch to a small group of real users and learn from what they do. The order matters more than the speed. Most money lost on first versions is lost by building before step two.
How do I describe my idea so a developer can quote it?
Describe your idea as one sentence in this shape: who has the problem, what they do about it today, and what your product lets them do instead. A sentence like that can be scoped and priced. “An app for small businesses” cannot. You do not need technical words, a specification or wireframes for a first conversation; the job of a good studio is to turn that sentence into a buildable plan.
If you can only write the sentence with “and” in it several times, you probably have two or three products. Pick the one people would pay for first.
Should I test my idea before building anything?
Yes. Before spending on a build, talk to people who have the problem and ask how they deal with it now and what that costs them. Then put up a single page that says what the product will do, who it is for and roughly what it will cost, with a way to join a waiting list or pre-order. If nobody signs up after you have sent real people to it, you have saved the price of a build.
A page like that is a small job. We quote a landing-page test as a fixed price after a short call, and it usually takes 2 to 3 weeks to design, build and launch.
What should the first version of a SaaS include?
The first version of a SaaS should include the one core job, done properly, plus the things that make it a real product rather than a demo: secure sign-up and sign-in, payments if you are charging from day one, the emails people expect (receipts, password resets, invitations), a simple admin view so you can run the business, and a privacy notice. Each customer's data must be kept separate from the start, because adding that later is a rebuild.
Leave these for later unless the idea cannot work without them:
- Native phone apps alongside the web app
- Detailed roles and permissions beyond “owner” and “member”
- More than one integration with another system
- AI features, unless the AI is the product
- Reporting dashboards beyond the few numbers you check every week
- Settings pages for choices nobody has asked for yet
A made-up example of cutting version one
Say the idea is a booking tool for independent dog groomers. Version one: a groomer signs up, lists their services and hours, clients book through a link and get a reminder email, and the groomer pays a monthly subscription by card. Version two, if version one sells: text-message reminders, deposits, a second staff member's diary, a client loyalty scheme and a phone app. Every item in that second list is reasonable. None of them proves the idea.
Should my first version be a web app or a mobile app?
For most SaaS ideas, a web app first. One codebase works on phones, tablets and laptops, there is no app store review between you and a fix, and customers can sign up from a link. Start with a mobile app when the job genuinely happens away from a desk or needs the phone itself, such as the camera, location or notifications while working. TradeLinkers, the trades app we built, is an Android app for that reason: the people using it are on site, not at a desk.
If you do go mobile, plan for the store accounts early. Apple's Developer Program costs 99 US dollars per membership year, and both Apple and Google require a company enrolling as an organisation to have a D-U-N-S Number, so check you have one before you need it.
How much does a first version cost in the UK?
From us, a first version of a SaaS platform with logins, subscription billing and an admin panel typically runs from £25,000 to £60,000, and a full mobile app from £15,000 to £60,000, depending on scope. A landing-page test is quoted as a fixed price after a short call, and can cost as little as a few thousand pounds. Freelancers usually quote less and larger agencies more; the comparison, with what each band actually buys, is in how much a SaaS platform costs to build in the UK and what a UK app developer costs.
Then budget for running it. On published list prices in October 2026:
- Database, sign-in and storage on Supabase: Pro plan from $25 a month.
- Web hosting on Vercel: Pro plan from $20 a month. The free Hobby plan is for personal, non-commercial use.
- Card payments through Stripe: 1.5% + 20p per standard UK card.
- Someone to look after it: see our guide to who hosts and maintains a web app.
How long does it take to build a first version?
A first version of a SaaS platform usually takes 10 to 14 weeks to build, a full mobile app 8 to 14 weeks, and a landing-page test 2 to 3 weeks. The biggest variable is rarely the code. It is how quickly decisions get made, how soon the wording and pictures arrive, and how much gets added once the work has started. A fixed scope agreed before the build is the best protection against all three.
What should I prepare before talking to a studio?
Prepare a one-page brief. It does not need to be polished, and it makes the first call useful instead of exploratory. Cover:
- The problem, in one sentence, and who has it.
- How those people solve it today, and what that costs them in time or money.
- The one job version one must do.
- How you will charge: monthly subscription, per user, per use, or one-off.
- What success looks like after three months, as a number you choose.
- Any system it must connect to, such as an accounting package or a calendar.
- Your deadline and a budget range, even a rough one.
- Two or three products you like the feel of, and why.
- Who will own the accounts: ideally your business, from day one.
On the business side, decide whether you are trading as a sole trader or a limited company, because payment providers and app stores ask. If the product will hold personal information, the ICO says organisations that use personal information, including sole traders, need to pay a data protection fee unless they are exempt; its online fee checker tells you which applies.
Do I need a technical co-founder to build a first version?
No. You need someone accountable for building it well and someone, usually you, accountable for what it should do. Plenty of first versions are built by a studio for a founder with no technical background. What you should not give up is ownership: the code, the database, the domain and the payment account should be registered to your business, so you can change developer, hire one, or bring in a technical partner later without buying anything back.
What happens after the first version launches?
After launch, the work changes from building to learning. Watch what real users do, talk to the ones who stopped, fix what gets in their way, and decide version two from evidence rather than the original wish list. Someone also has to keep the product running: hosting, security updates, backups and monitoring. Our guide to hosting and maintaining a Supabase or web app in the UK covers what that involves and what to ask for.
How does BozApps work with founders at the idea stage?
Send us the idea in a sentence through our idea form. An engineer replies within one working day with a suggested scope, a timeline and an indicative cost, and we are happy to sign an NDA before you share the details. If it is a fit, you get a fixed price in writing, weekly demos on a private preview link while we build, and everything registered to your business. We can host and run it afterwards, or hand it over. More on how that works: turn your idea into an app and build a SaaS platform.
Where do these facts come from?
- BozApps prices and timelines: our published pages for SaaS platforms and ideas to apps.
- Supabase pricing and Vercel pricing. Checked 24 October 2026.
- Stripe UK pricing. Checked 24 October 2026.
- Apple Developer Program enrolment and Google Play developer account requirements.
- Data protection fee, Information Commissioner's Office.