Recommendations on physical server to buy to run small scale VPN?

I'm the IT technician for a small company that for various reasons requires a VPN into their physical in-office network. Has to be a physical computer, can't be via a cloud provider.

Am currently looking at a purchasing server that can serve up to 30 concurrent users connected to the network at once. I've set up VPNs before but not at this scale, so are there recommendations on what to look out for? Is there a go-to general purpose rack server that works for this? Learning by doing right now :D