Help me in building a vpn android app with backend

I want a vpn android app source code with at least 20 different country servers. The app when published on play store should be able to handle 10Million+ users. The pricing of the servers should be the minimum. I want all the backend of my own. You would have to guide me in setting up the backend if required. I do not want to be dependent on anyone for services for my vpn app like cloud setup, domain, hosting, etc.