I've talked to the local zoning board and it looks like I can legally
convert the attached garage and storage area on my rental property
into a one bedroom in-law apartment.

My next step is to get an idea of what it would cost.
The garage has no plumbing at all.
I'm just making wild guesses, but I'm thinking $5k to hook into the
house's water & sewer, $5k for a 1/2 bathroom, $10k for a small
kitchen, $5k for wiring and electric heat.

Really, I'm just pulling these numbers out of thin air.
Has anyone here done this type of conversion?

Vin - Menotomy Vintage Bicycles
http://OldRoads.com