What billing systems exist for organizing VPN billing?

Question

VPN

Hello!
In connection with well-known events, a business idea came up - to place servers in China and other countries and sell VPN services through billing. It would be desirable on the basis of OpenVPN, but others are possible.
Advise on billing solutions?

Answer 1

Asmodeus - a friend was engaged in billing systems 15+ years ago, he just has a ready-made solution - high-quality and inexpensive.
I sincerely recommend.