Any SaaS to easily monetize my sideproject?

I've created a sideproject (website) that I might want to monetize. But I would have to add capabilities for user-signup, a website for payments/plans, customer-support and so on.

Is there a SAAS that creates all of that for me while being developer friendly, just offering a nice API that I can integrate, e.g. not forcing me into using a framework or a certain programming language?