Hi, Dominic,
If you just want to build one project then you could probably do it in a class. That's great becuse you learn and get your thing at the end, too. If you want to do this at home then one of the most versatile rigs is an oxyacetylene torch. You could pick up the whole outfit for $500. Cheaper would be a little buzzbox welder, but these are limited in their capabilities. Of course, you will still need to learn how to use either of these! A class would be a good thing. If you are really limited to your basement and don't want to burn down the house then you should probably find somewhere outside to weld. You could do TIG in your basement, but this is expensive.
As for tubing, look in your yellow pages under metal or steel and you'll find the places. The best thing to do is draw out the project and then get the shop to cut the pieces (unless you have the tools yourself and want to save money -- it is pretty cheap to get them to make the cuts). Note that you cannot get any of the steel stock or welding equipment at Home Despot, etc. aside from really small stuff.
Hope this helps -- enjoy!
Chris