I think fiance is cheating on me.

Ok..so I am not sure he is physically cheating on me but let me explain. He looks at porn (I dont like but I deal with it) but lately he has been getting into web cam girls. He wastes a lot of money on them and does the private chat and emails them. I know its their job- but I think that is cheating. He also knows a woman in NY who he met through work. They CONSTANTLY flirt emails back and fourth. Some of it sounds like they have been planning to meet for sex for awhile but for whatever reason it hasnt happend (maybe because we live 300 miles away?). I dont know why he is doing what he is doing but this is all new. It hasnt happened until maybe 1.5 years ago (weve been together for 5). I just am saddened and do not want to be played for a fool. Part of me wants to marry him, then divorce him so I can get half of his money (the best revenge). If I bring it up, he will call me out on snooping (which I am guilty of). But the truth is, I dont really care anymore, I clearly do not trust him. I thought about leaving him now, but there is too much time, effort, money etc.. into this relationship and my family lives 2 hours away so I can't just move there- my job is here. I cant afford to live on my own....so I would be jobless if I move back home. What do I do??
My parents both lost their jobs, so they cannot support me either. I am 24.