Came across this thread as we are now also considering a garage apartment in the Heights. In fact, we have an existing structure but by the time we remediate it and bring it up to code (basically untouched since 1940s) I think we may be looking at a full rebuild.
Considering in 2009 the cost was +/- 80K what are we realistically looking at today?
20 x 30ft 2 story structure. Double garage on lower level, 1 bedroom, kitchenette and bathroom on second story.
Cheers!