Build the smallest useful tool.
This problem did not need a custom backend or weeks of engineering. A focused utility could provide the value faster and with less friction.
Personal finance · AI-assisted utility
Before You Buy
A privacy-first cash-purchase tool that tests affordability against an emergency reserve, then translates price into time, ownership, and use.
Before You Buy
Live resultComfortably affordable
Your numbers stay in this session · Nothing savedThe problem
I care about living within my means and avoiding consumer debt, but I can still overthink larger purchases. A bank balance alone does not answer whether a purchase is comfortable, responsible, and genuinely worth the time it took to earn the money.
Built for
- Thoughtful buyers who want a clearer affordability check
- People who tend to overthink larger purchases
My role
I defined the problem, shaped the decision flow, and used ChatGPT’s Sites feature to turn the idea into a working utility quickly.
Built with
The build
Turning the idea into a useful product.
- Translated my own purchase-decision process into a short flow built around price, liquid cash, essential expenses, and a chosen three- or six-month safety floor.
- Prompted and iterated on the experience using ChatGPT Sites instead of starting a traditional software project.
- Added optional perspective for income, expected ownership, and use frequency without making the core affordability check feel like a long questionnaire.
- Turned the inputs into a clear verdict supported by cash remaining, emergency runway, safety-floor margin, liquid-cash usage, gross work hours, and ownership cost.
- Made privacy part of the product: users can enter personal financial details without that data being collected or stored.
The boundaries
Constraints that shaped the work.
- No accounts, saved history, or personal-finance database.
- The experience needed to be useful in a few minutes, not become another system to maintain.
- The recommendation should support a decision without pretending to replace personal judgment.
Decisions & tradeoffs
The choices behind the product.
Collect no personal financial data.
People should be able to answer sensitive affordability questions without wondering where their income, savings, or purchase details are being stored.
Consider value as well as affordability.
Being able to pay cash does not automatically make something a good purchase. Work hours, share of income, expected ownership, and frequency of use provide a more honest perspective.
Making it real
Validation, safety, and delivery.
Validation
- Walked through different purchase, cash, expense, and safety-floor combinations to verify that the verdict and supporting calculations respond clearly.
- Checked optional salary, work-hour, ownership, and usage inputs to make sure they add context without blocking the core result.
- Reviewed the experience as a quick mobile utility rather than a long financial questionnaire.
Security
- The tool was intentionally prompted and designed not to collect or store the financial information users enter.
- No account is required to use it.
Deployment
Built and published with ChatGPT Sites as a fast path from a personal problem to a usable public tool.
The result
What came out of it.
Before You Buy turns a familiar moment of uncertainty into a live verdict, such as comfortably affordable, then shows the numbers behind it: remaining cash, months of emergency runway, reserve margin, cash used, gross work required, and cost over time. It also demonstrates that good problem solving sometimes means choosing a fast, lightweight tool instead of fully engineering a product.