Actually, on a more serious note, one thing you could do is pour a concrete pad.
I bought a home that had an existing concrete pad in place (done by the builder / developer).
When it came time to build a garage, I didn't have to worry about hiring a concrete company.
I think this could be attractive to potential buyers.
Double Detached Garages can be done for a fraction of the cost a garage builder would charge.
This I what I did.
1. Bought a Garage Package at Totem (just the lumber and the garage door, windows and man-door).
2. Bought pre-fabricated trusses separate from a truss maker
3. Bought Siding direct from a suppler (Mitten)
4. Bought Shingles from Roof-Mart
5. Paid Framer, Paid Electrician, Paid Sider, Paid Roofer
My total cost came in at $9,000