Will you be servicing the loans? I assume you will be if you are going to be doing the audits. FNMA and FHLMC require Quality Control reviews. You can find what you need in the guide books. My bank uses a website called www.allregs.com
You have to be registered to use it, but there is a lot of information on there as to what you need to do.
Hope this helps....you may also want to contact your CPA firm. They may be able to give you guidance.