How do I get started with building a landing page with a payment option?

I inadvertently stumbled upon a DaaS opportunity when helping a local business set up their tech stack, and since this problem is scalable, I think it's a viable idea as a side business. Unfortunately most of my (admittedly very little) experience is backend, so I haven't got the faintest idea on building a landing page. The last landing page I built was hosted on github and was basically just a rehashed version of another website's template. Can anyone give some advice as to how to do this? I guess integrating Stripe is a pretty straightforward task after the initial build.