Check on eBay for steel buildings if you want to do it really economically. I bought a 25 X 30' steel building kit for $4,000. They are engineered to go up with hand tools. Not the prettiest things in the world, but you can 'skin' them to match your architecture.

A couple reasons really. You might not be able to tell from the picture, but the garage is about 5 feet above the level of the yard and the retaining wall was already in place. So it would have been a lot of earth moving and relandscaping.

And I don't really like the lack of convenience of tandem garages. You either only drive one car, or you have to shuffle them to get to the other one.

I'll try to take some pics of the inside - but it's not too impressive. The ceiling is open to the peak (commercial roll up door) which is 15 feet and the walls are 10.5 high so it feels a little bigger than it really is. 22x22 isn't a lot of space when you get a couple cars in there -but it's a pretty good size compared to the rest of the neighborhood.