Just setting up a betting server is totally free, just make a server, set the rules and give it a catchy desc.
But to make it run good most people global their servers (http://forum.toribash.com/tori_broadcast.php), this costs 10k for normal members, but you can ask any toriVIP to do it for you, and you'd save 5k. Next to this some people tend to have a starting decapprize of about 1-10k.
So that makes about 10-20k to start the server, once it's become populair you'll earn that back in no time, but it's not guaranteed.