I swear by these:
http://www.northernbrewer.com/default/20-gallon-megapot.html
Using a handful of stainless nuts and bolts as standoffs, you can have a false bottom made of
this perforated sheet for around $69.
You can get away with one pump even on a single tier stand if you batch sparge.
www.bargainfittings.com has the best prices I've found on stainless hardware (valves, cam-locks, fittings, etc).
I recommend 1/2" translucent silicone tubing. I get mine from Austin Homebrew at around $2 per foot.
You won't find a cheaper brew stand than what Yooper mentioned above. Even the materials to weld one (or build one out of wood) yourself will likely cost as much as a
Gorilla Rack or similar shelving system. If you have a bunch of scrap steel tubing or angle iron laying around, the price of a self-made stand will significantly drop.
You can split a single Gorilla Rack like the one I mentioned into two workbench-height units that would be more than wide enough to hold three kettles. Costco and Sam's Club usually have good prices on similar shelving.
To keep your project under budget, the amount of automation will have to be minimal. I don't have much experience with PID controllers, but they aren't usually cheap.
This site has great prices on PID controllers, SSRs, and thermocouples. I haven't ordered from them or used any of their products, but the prices are outstanding.