I guess it all depends on what you want to get out of it and if you are able to reach the goal you set...
Like I said, becoming an affiliate for the specific casino you wish to promote takes just a few minutes, but successfully promoting them can take a long time.
I am still new to the whole thing, but making money isn't really my objective. If you remember the "beckett" days (http://www.beckett.com/userpages/gprix33.html), I only started that site to make my contribution to the whole ND thing. Then I began to get a lot of traffic, so I kind of felt obligated to take it to the next level. That's where I stand now. My basic goal is to provide a clean and crisp site (banner free!!!!) for everyone. I have got nothing but great feedback, so I think I am doing alright so far.
As for costs, I suppose it all depends on which method you decide to promote with. Way back in the "beckett" days, I didn't even use affiliate links, but I thought I could use any revenue made to improve this site.
Running a website like this has some costs. The domain name is a yearly fee for me, hosting for the site is monthly, and live chat is $99/month.
More importantly creating a website can be a lot of work, as I am still no where near done with this one. However, I think it's kind of a neat hobby, and it always makes me feel good when I get positive responses from everyone.

Sorry to keep talking, sometimes you just can't stop!!
Hopefully that answers your questions, but feel free to ask another if I missed anything.