My advice would be to go ahead and buy a rack to see how they've done it, and then if you can tackle the job, build your own. That's my plan. I've bought a great rack from http://www.herpenclosures.com and i saw how easily it is to put together and where everything was put, and now once i get my hands on the proper tools, i will build my own. There are plenty of companies that build racks. You just need to figure out what system will suit you best. Animal Plastics, Herp Enclosures, and i hope someone will post more links

If you think you're capable of handling it on your own the first time, here's a great DIY from Tim Bailey

http://www.baileyreptiles.com/diy.html