Hello, i have been an owner of 2 raspberry pi’s and i want to know is it possible to host a server on a pi 3?
gday mate! 
you absolutely can run a server on a raspberry, since server specs are irrelevant, cos every CLIENT renders vehicles for THEMSELVES, the server is only sending players’ POSITIONS, which is AFAIK dependant on single-threaded CPU performance? the only requirement, really, is “a low latency and enough bandwidth, about 4MByte/s combined in/out”. pretty sure any distro will suffice. obviously, you will be compiling from source, as pretty much anything on arm, lol.
now, if you want to combine your two pi’s into a cluster, you will need to have two things: a compute module 4 io board and a pi zero. could be a bit costly though than just renting a VPS, though.
good luck and be well! 