
Learn how your prospective customers behave, the problems they need to solve, and what frustrates and delights them. These insights may shake your assumptions, but they'll help you reach the "ah-ha!" moments that inspire truly great products. Lean how to: validate or invalidate your hypothesis by talking to the right people, learn how to conduct successful customer interviews play-by-play, detect a customer's behaviors, pain points, and constraints, turn interview insights into Minimum Viable Products to validate what customers will use and buy, and adapt customer development strategies.
Lean Customer Development by Cindy Alavrez is a book that has details.
Edit: some jurisdiction these restrictions don't apply. That is: your off clock works cannot be claimed.
Not a Lawyer.
I'm not in your target market, so I don't have anything interesting to say about the product itself, but I do have some suggestions for how you can get actionable feedback to de-risk your project:
First, you don't necessarily have to actually charge money in order to find out whether people would pay, you only have to measure whether they click a "buy now" button (or the equivalent).
Furthermore, while the folks who clicked the button might be slightly annoyed that the button was "fake", they are then good prospects to sign up for notification when the product is available for purchase, and are decent candidates for user testing your eventual product (but keep in mind that the product you develop based on this sort of validation may be different than the one they tried to buy (also, the more-annoying variation that is actually taking the order and then cancelling the charge is pretty risky unless you use a throwaway business/product name, I've never tried that and wouldn't suggest approaching those folks for anything else).
Creating and A/B testing google ads and landing pages will (potentially) teach you which users to target, what features/phrasing potential customers find most compelling, what pricing models to use, and so on, helping you to hone your value proposition and prioritize features (fair warning, you may learn that there is no viable market).
There are a lot of decent articles on the web about validating an idea with 'spoof landing page', 'dry wallet', or 'fake door' MVPs, but some of my favorite resources are the following books, which will also give you good context for these and related tactics, as well as 'next steps' you can take:
Running Lean by Ash Maurya
Validating Product Ideas Through Lean User Research by Tomer Sharon
Lean Customer Development: Building Products Your Customers Will Buy by Cindy Alvarez
Customer development is WAY MORE important than product development (as you've just discovered)
Solution Selling by M. Bozworth