I completely understand. I haven't had any steady work in three years; right now the best I can do is odd jobs and handyman type stuff, because relocating to find work isn't an option. The last big income I had I spend a couple hundred US$ to upgrade my hard drive, video, power supply and RAM. This system was a hand-me-down from one of my sisters; it started life as an HP Pavilion that caused her a problem and the repair guy she took it to replaced the power supply and the case. Then a lightning strike fried the motherboard so she replaced it, the CPU and the RAM (this is where she and I first encountered Ubuntu as the new motherboard came from a 3rd party supplier and wasn't HP branded, so her HP-branded XP restore disks wouldn't work). Then she bought herself a new HP Pavilion PC and gave me the old one. She never got comfortable with Ubuntu and was happy to return to a Windows PC - although she complained about Vista not being like XP.
I like it just fine and the cost to me (then) was $0! With all the work that I've done to it since 2006, the HP part is just a fading memory, as there are none of the original parts remaining. I mentioned it has the single core AMD Athlon 3400+ 64-bit CPU and 2GB RAM; I added a 500GB SATA drive, a nVidia GeForce 9500GT PCIe video card that has 1 GB VRAM, and a 600W power supply. If I were doing it again I'd probably spend even more money on it by upgrading the motherboard and CPU to a faster multi-core processor, more RAM, and I'm dying to dump my CRT for a flat panel!
When I do get ready to buy parts, I generally check out NewEgg.com to see if they have any "bundles"; we got this CPU/motherboard/RAM as bundle and I think it was under US$130 including shipping. It was relatively inexpensive because it was (at the time) previous generation hardware. The motherboard was designed to be used in an office - the so-called nVidia Business Platform. Works pretty good for me, though.