Table of Contents Key TakeawaysDTI limits aren't fixed — FHA allows manual underwriting up to 50% back-end DTI for buyers with strong cash reserves or credit history.Loan type changes your student debt math — Fannie Mae counts a $0 IDR payment as $0, while Freddie Mac/FHA add a phantom 0.5% of your balance (~$400/month on an $80K loan).Self-employed buyers qualify on...