sandblasting guns on ebay and auto painting.?

[Nicole E]

My husband and I just purchsed a horse trailer. It is steel and has some rust on the roof and other parts of the trailer. We want to sand it down and repaint it and are looking at sandblasting. Ebay has a "sand blasting gun" that you hook to a 5HP compessor, would this work to lightly remove the paint and rust?
We are then going to prime it and then put an enamal auto paint, probably white b/c we think it might be more forgiving then a darker color, my dad owns a spray gun.
here is one of the ones on ebay...
http://cgi.ebay.com/SAND-BLASTER-GUN-TIPS-Sandblasting-NR-Air-Tools_W0QQitemZ120161164602QQihZ002QQcategoryZ4357 0QQrdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247 QQcmdZViewItem
has anyone used something like this before? we would only be using it once, and just want it to get the rust off...
the local body shops are charging $500, we don't really care how long it takes, but cannot afford that...