Originally Posted by Sheep221
Don't buy some shit old stuff there.
Whoa there... I don't know where you live, what weird laws there might be, but north of 49th, it's free.
Most garbage dumps have a section near the gate where you leave things like PCs, TVs, Microwaves... may or may not be functioning obviously, but free if you want them.
There's also usually at least one (words failing) dedicated electronics place where you can drop off your old equipment, some of them specifically for computers, where you can get a fully working system for next to nothing, occasionally nothing, or by bringing in your own stuff as trade.
Nevermind garage sales, and so forth. I don't see the point in buying a new system when there are plenty of used ones that are more than enough, and you won't be that bothered if/when they die, or you spill oil on them or whatever.
No offense to the OP, but it's not exactly a lab coat environment. The older the equipment the better usually, it's tougher, simpler, easier and cheaper to fix.
An even older system that mentioned so far might be better, if you can get a motherboard with an ISA slot or two, you can create your own expansion cards with rudimentary soldering skills and junk parts. This was, and still is done in CNC/CAM, should be possible with LinuxCNC, is possibly with TurboCNC and the likes, and you can still buy new motherboards, even Ivy Bridge, with ISA slots for that reason.
If OP wants to go the money-route, get a Toughbook or similar, and one of these
. Durable enough to drag around the shop, easily enough power (i5's, GB's of RAM, etc), disconnect use it for whatever else.