Control panel for VPN hosting?

Question

VPN

Hello. I am very interested in whether there is any free control panel on the network with which it would be possible to organize something similar to VPN hosting.
Everything is required outrageously simple, without design:
1) user registration
2) payment of the tariff + receipt of goods (key and certificates)
3) after the expiration of the tariff, so that I receive a message in the mail (or something else) that the user has not paid for the next period.
Maybe it's possible to somehow modify some ready-made PU for hosting to suit my needs?

Answer 1

Very handy vestacp.com under linux.