How can I manage users on my VPS hosted Flask website

Question

I'm building a website, but I just encountered a problem that I have not been able to solve:

I have a python flask app as well as several HTML files that make up my website, hosted on a VPS

The problem is this: I want visitors of my website to be able to create accounts on my website and I just can't make this work. The idea is to add billing later on for a "premium" plan

How can I make this work?

I need users to be able to create accounts and I need to be able to charge them money. Keep in mind that all of this is running on a Ubuntu VPS and the main code is a Python Flask application

These are some ideas I came up with:

• install wordpress on VPS
• install wordpress on webspace and have a headless python script, communication via API
• use SQLAlchemy in Flask app