quote" I have heard that it isn't good to put bedrooms above a garage due to possible rising fumes. "quote

That, my internet friend, is HOGWASH.

I'd suggest getting an architect first and start searching for a good framing carpenter. He'll be harder to find than the architect will. Don't sign with any framer until you've previewed his work and spoken with some of his home builders. If he shows any apprehension about these requests, look for another.

just my .02

See Ya,
Kelly

Depending upon the age of the house and the way the slab was poured in relation to the sill plates you might need to do structural work first to repair damage to the wood on the concrete.
Ron

does your garage have footings able to support a 2nd floor? I live in MN and we need frost footings that go down 4+ feet below grade. an unattached garage does not need them and can be built on a slab with 12" deep perimeter footings. a nice rambler near me had a garage about 15' from the house and the owner built a breezeway? so the house/garage is 1 unit now. I always wondered what type of footings were on the garage.