If you extend the garage build a cottage on top of it you can rent it out for some extra saport. That's what my sister in law did with hers home when she re-molded it she did it where she section room's off. She rented the house out with four different renters and she lives some where else those renters pay for hers living, she's retired and invested well.
We had talked about doing an apartment above the garage before, but there are several issues. First off being the garage was built before the city was incorporated and is not up to code, so if we wanted to add an apartment on top, we would have to rebuild the entire garage. The second issue is cost.