If you're working with a good Realtor, you may start by discusssing the situation with some of their contacts.
As Helen from Torrance said, small community banks and credit unions are good places to talk to also. Working with a banker that you have a relationship with can be extremely helpful, since they make their decisions "in house" in a loan committee. Having someone that knows you more than just a paper application is nice.
The problem with this type of loan is that because they don't follow the guidelines of a larger investor, they can change frequently. A bank may be willing to loan in January, but due to its own financial position, may not do the same exact loan in March.
Best of luck to you and feel free to contact us for some great mortgage referrals in St Louis that do portfolio lending.
Dielmann Sotheby's International Realty
A portfolio loan is often available through a mortgage broker with multiple sources, local banks who service their own loans and possibly US Bank.
The underwriting guidelines are different, there are often fewer choices of programs and rates may be higher than what is commonly advertised by conforming lenders.
If you need help contact me through my website and I will locate an agent in your local area to help you.