I may know a little about this

Firstly get the free hosting idea out of your head if you want to run a torrent site/forum. If it grows in popularity then at some point your going to have to go for a dedicated server so you may as well go the dedicated server route from the beginning. You dont have to go all out and get a dear server as your hosts should be able to upgrade you if & when you ever need it. Budget about £40-50 month for a dedicated server.

If your site/forum is going to have torrents attachments then dont get a server from the USA or UK for obvious reasons. Go for European hosting with a country where the copyright laws are a little more relaxed ie Netherlands or Sweden or you could go for offshore hosting like China, Malaysia etc but support from these countries can be a little slow with language barriers etc.

The most popular forum software to use is either IPB or vBulletin. Both of these you need to purchase then pay a yearly fee to keep getting updates or your site can become more open to hackers and little script kiddies.

Starting off your own site isnt easy and you will need knowledge or someone with know how on setting up your board for you and maintaining it.