I am purposing a full installation of L2TP, PPTP, OPENVPN in one server with freeradius.
Username and password can be added from mysql database or file.
Not same thing, with this configuration you can launch your own VPN Business.
D you have a guide for integrating this with freeradius / whmcs?
Installation include integration with freeradius (The script will install OpenVPN, L2TP, PPTP + Freeradius).
All combined, and you can add username + password from MySQL database / Or file like you want.
For WHMCS not using it but if you have addon it will be easy.