Tobin-

I've done what you've done TWICE in my life.  Both times I set out to build
a garage myself, but discovered to my surprise that I could get a better
deal from a garage company.  You may think "I don't want any prefab junk"
but in fact there are companies who build very good garages for less than
you can yourself.  They can get components such as doors much cheaper than
you can buying retail. Examples:  In 1990 I had a company called Coach
House Garages (based in Illinois) build a 3-car, 2-door,  34x22 beauty 
(with special 7 1/2 ft. door height so a VW camper would easily clear) for
less than $8000.  I talked to one of their reps a couple of years ago and
that same size garage was still only about $10000.  That garage was one of
the main selling points when I sold that house.  

Long ago, in about 1980, a company called Bullock Garages built a decent
garage for me (1 1/2 car) for $2700.  The cost to have a footing dug and 
the concrete poured so I could build my own was half of that.

Don't know what part of the country you're in (I'm in St. Louis) but check
the yellow pages in your area and see who is in the business locally. 
Costs do vary hugely from one part of the country to another.   All the
outfits I dealt with pretty much let you design the layout, choose door
type, window type, etc.

Bill