Adsense Placement? (and something else)

I'm sorry if I sound like a basic, but heck gotta learn somewhere.

Question #1:

I'm new to the adsense. I've never used it. Well, except for at a blog from blogger, but that's just basic becuase it has an automatic placement.

When using adsense is there issues with putting in into your site. For example, Is is just a simple code that I can just put where I want or is there often, rules, difficulties with placing adsense?


Question #2:
Does Adsense always deliver more profit than hosting charges. I recently wanted to get a hold of a forum hosting service(basically like invisionfree, Probaords, Conforums, etc.). This is where you host forums for free and the forum has adsense banners at the top. Now when I realized that I'll probably be able to get the place huge, I got really bothered because I don't know enough about adsense.
If I were to have this site, it would cost a lot to host it, and I'd probably get like 50 free forums registered, then the admins of these places would go and run off finding members whom would take a lot of bandwidth.
How can I be sure that adsense will beat the cost of running it.
Is there ever any sites that end up costing more than it's possible to make?

I want to profit, not pay more.