It is possible! You can run as many websites as you’d like on your VPS as long as your specs can handle it. 
You will need to run Discourse behind a webserver / reverse proxy like nginx to be able to host multiple websites on the same vps. Here’s a very good guide on setting nginx + discourse up: Running other websites on the same machine as Discourse
These are the hardware requirements for a Discourse installation, obviously if your forum gets more traffic you might have to upgrade your specs, but you don’t have to worry about that for now.
- modern single core CPU, dual core recommended
- 1 GB RAM minimum (with swap)
- 64 bit Linux compatible with Docker
- 10 GB disk space minimum