A lender will pull your credit from 3 credit bureaus, and will use the "middle" FICO.
A 620 isn't a bad score, and I believe FHA has recently removed the requirement to pay minor debts.
An excellent lender in Apple Valley is Roy Quintanar at Alaska USA Mortgage. You can contact him at (877) 722-8919.
Do not hesitate to contact me with any questions you may have.
Bo Goulet, cdpe
Certified Distressed Property Expert
Shear Realty-Spring Valley Lake
12170 Spring Valley Pkwy.
Victorville, CA 92395
Mobile: (760) 713-6137
Fax: (760) 243-4552