$309 Side Mount Murphy Bed / Wall Bed Hardware. (Twin, Full/Double, or Queen all $309) Includes instructions for basic cabinet construction + instructional DVD.
Sled Finished Sled
If you have a welder there are a few more things you can make on the cheap. Here is a pull sled I made.
Convict Conditioning Push Up Progression | 10 Steps to One Armed Push Ups
legraises Convict Conditioning Leg Raises Progression
I don't know about this, but it would be a cool trick -- Convict Conditioning Bridges Progression
Handstand Push-Ups - Body Weight Training Arena
Dips Progression - Body Weight Training Arena
Pistol Squat Progression | Body Weight Training ArenaBody Weight Training Arena