Often, mortgage brokers will have the most programs available to them. Below is a link to a broker that works in Milwaukee too.
Michael Collins- SFR, BPOR
Rock Realty Wisconsin
My Trulia Blog:
Banks typically use the middle credit score of the lower borrower. If you intend to rely on his income, he will need to be on the loan. Lenders are extremely cautious these days. The credit score the bank will use will be the one that either they pull, or the one pulled by your mortgage broker. Generally if your score is 740 or above you will get the best rates and terms available. If it dropped below that a bit, it may not matter too much.
In order to qualify for two mortgages at the same time, you will need enough income to handle both and meet the lenders debt ratio guidelines, around 45% of your gross income or less. If you have the other house rented out, 75% of the rental income could be added to your gross income for the calculation.
You probably should meet with a lender in your area right away to go over your boy friend's credit and see if there are steps he can take to improve his scores. Best of luck.