Here is what I have. It's 12' wide x 20' long. 8'high.
Mine is the one with the sloped roof not the round one. Thats where my Roadrunner lives

. The only problem is the condensation that build up. Cold at night warm during the day makes bare metal parts rust. (Like my Factory manifolds,tie rod ends, etc. BUT it is better than nothing.
I paid $750 for front and rear roll up doors. Ive had it for 5 years and not a single problem. It's gone thought 3' snow storms, 80MPH winds and its still standing.
http://coveritshelters.com/residential/res_1car.html