You could get something like this. It retails for $26.86 at Walmart, it would easily hold tubs or tanks depending on size, plus room for supplies and other stuff. Might be a nice and very cost efficient option for you. It won't give you all the benefits of a rack but it could be a good alternative for your needs.

http://www.walmart.com/catalog/produ...uct_id=2123448

You can order pre-wired flexwatt and so forth from Rich at www.reptilebasics.com Flexwatt is a very efficient and safe heating option plus it's easy on your budget.