You should be careful when you're selecting a VPS, many companies will incorrectly advertise how many bots you can run on their server.
If you want to run 6 bots you should be looking at a VPS that has at least 3-4GB of ram (this might get a little costly :/).
Also I recommend purchasing from a site thats setup specifically for runescape botting as many other VPS companies don't allow it/don't offer a virtual desktop and if you do it'll typically come with the most common botting software/java pre-installed.