Twitter is very very saturated, but that doesn't mean you can't make money, it just means you have to do more work. I'm sure earlier on it was as easy as auto following and throwing a link out there, but now you have to filter through all the crap and follow the real users. Like someone said above, follow people who aren't putting links in there tweets.
My Twitter has almost 3k followers, and they all are pretty much throwing links non stop so my account is pretty much worthless. I think maybe 3% of my links get clicks and 0% convert. So yeah take your time and do it right and it should pay off more in the end.