Hey Curt,
Add up everything you think you might need, then times it by 3. That's what I've invested already, and the end is not in sight. Not including tools, I'm in for an easy $500.00 so far, and I've got a nice sled (almost). Luckily I have a cousin who has spent a few thousand dollars on a mill and lathe and is doing all my work for free. I've been buying him mill bits, aluminum stock, and beer

One day I'll have to find a way to repay him, he's saving me a ton of money.
NOTHING can hang off your rig. Period. Anything that is attached to your camera must not touch anything else or it will become unbalanced. Just by removing the lens cap, your rig will be off-balance.
There is no reason to shot en entire film using a steady-cam, unless that is really what you want to do. Tripods, dollies, and handheld shots fill up most of the production work done in movies today. I just watched a feature film this weekend, and saw maybe 2 or 3 shots that were done with a steady-cam. The use of the steady-cam should be so you do not notice that it was done with a steady-cam.
Best advice I can give is this: If you think building a rig will be more of a burden than a benefit, don’t do it. Buy one

I'm having lots of fun building my rig, but I'm kind of strange anyway.
Good luck!