Fiance & Marriage Visas: A Couple's Guide to U.S. Immigration
explains it all quite well under the 2009 system, including a chart of figures at the end. It won't be exactly the same but at least an idea
You need 125% of the poverty guideline if I understand this correctly, so if there are only 2 of you in the house it is an income between $18,212 and $22,760 depending what state you live in. I imagine you also need a few hundred $ to file all the paperwork, possibly a couple thousand for all the legal costs involved with it.
I am not a US citizen, nor have I been through this, this is just what I found on the above website , so I don't know if I got it right so don't do anything rash just on this advice
