Is it okay to launch on PH, without the actual product, but with the option to pay for that?

Hello hunters! I have a dilemma. Im launching an educational product, which production will take like a month or more. It's a fintech hub, which will allow folks to dive deep into the fintech industry, business models, growth cases, how to launch, and even more. Link — learnfintech.xyz So I wanna test demand in this kinda product before I start production, so as not to waste a lot of time. I talked with product managers and founders who launch courses, and other educational stuff and they told me the only way to test it — collect payments before launch. Waitlist won't show anything. 1) Can I launch on Product Hunt, collect payments, and then start making the project? So this way I'll test the hypothesis, and It will be covered with payments, so I will know people want this thing truly. And then I'll start building it. 2) Second option is — to build like 10-15% of the product and then launch, so people will have something as proof of the product and what they got at the end. Share what you think, folks. Really appreciate your opinion!