Called 11 lenders about ADU income, four count it, all with different haircuts

I'm not buying yet, so this is a paperwork win rather than a deal. I spent three weeks calling lenders to find out who would actually count projected income from an accessory unit toward my qualifying income on a one unit purchase, because the agency rule existing does not mean the shop in front of you will do it.

Eleven calls. Four said yes and could point me to a page. Three said yes on the phone and then went silent when I asked for the underwriting matrix in writing, which I'm treating as a no. Four said they don't do it at all.

Of the four real yeses, here's what differed. Two required the accessory unit to be legal and permitted on the county record before any income counts. One would work from an appraiser's rent schedule with the unit as-is. One applied a 75 percent factor to the appraised rent, one used 85 percent, and the other two wouldn't commit to a number until they saw the property. All four applied the cap limiting how much of my total qualifying income could come from that unit, and all four described the cap consistently, which was the only thing they agreed on.

What I got out of it: a fully underwritten pre-approval, not a letter off a soft credit pull, that moved my workable purchase price up about $62,000 compared to the same lender's number without accessory income. Sixty-two thousand dollars in a market where that's the difference between houses with a rentable space and houses without one.

Terms move and overlays change, so anyone doing this should get their own lender's current rules in writing and not build a search around mine. What I'd keep is the question I ended every call with: send me the page. Four people could.