Honestly buying a bender really depends on how many bends your planning on. A bender can run from a few hundred to easily a few thousand
I personally just purchased my second bender from Affordablebender.com @
http://www.tjdieselperformance.com They work great for the $300 that they cost. They are fairly small and don't take up a ton of room when not in use. This is about the cheapest way to get bending tube that I have found out there. The major draw back is that they have bend large radius bends, so sometimes its a bit of a hindrance in your design
If your planning on doing lots of bends I would spring for a JD2. You can add digital read outs, degree rings, hydraulic conversions that will make bending more repeatable and easier.......the sky is really the limit, if your wallet can handle it.
I would strongly reccomend getting a copy of Bend-Tech pro. It is a bit expensive up front but it will save you tons of $ in wasted tubing. Think as the software as in investment. One of the nicest things about bend-tech is digital tubing is free so you can play around with the part and try different ideas for free. Its a very user friendly program and is easy to figure out even if you dont have any CAD experience. Plus if you have any questions their customer support is out of this world! One of the few A+ companies I have dealt with.