Well I guess I cannot edit my orginal post but here goes.
The bottom measures 30x30, the center post is 42" tall and the upper frame is 12x30. I did cut the upper frame on a 5 degree cut. Everthing is 2x4 except the portion right in front of the bottom of the door and I used a 2x6 with a 1x2 for the door to rest on. I did notch cut the bottom and upper frames and vertical support, probably could of gotten away from doing this. But if figured it would give it a lot more strength. I purchased a small set of swivel casters with rubber wheels and it works good on the concrete floor. I did cover all the boards with some outdoor carpet. I had the screws at home but I have less than $40 including the carpet.
Material list (all from lowes):
Box of 1-1/4" wood screws (for joining the notched 2x4's)
Box of 3" wood screws (for the joining the 2x6 to the 2x4's)
4 small swivel rubber casters.
1 bunge cord to keep doors held in place.
Awesome, thanks for posting this. I'm going to build that this weekend, but with a modification to allow me to put the rear doors on as well - probably on the inside, requiring me to extend the cart outwards slightly. I'll let you know how that works out.
Hold my beer and watch this.......
Let me know and post some pictures, I might be doing the samething for the girlfriends 4 door also. Something that could be done is like you said to widen it some and add 2 more vertical supports one on the end. You would then end up having two doors face each other on each side. Might get pretty long though.