Doing electrolysis yourself is not an easy task. You need to be dedicated enough to learn how to do insertions properly to actually kill the hair and not scar yourself. This can take a while and requires quite a bit of patience. Most people don’t have it.
The most basic cheap machine that works is One Touch. Other than that, you’re looking at a used professional machine. There is an entire thread on the forum that’s called “Legitimate electrolysis machines for sale on eBay”. That’s what Christine is referring to. Even if the links are dead, the names of the machines are still valid. Plus, that thread is being updated continuously. The best way to ask your question is to post the names and links of machines you’re considering there so professionals can take a look.
Btw, with $500, you can get 2-3 professional treatments on your legs which could get rid of up to 70% of your male leg hair. I had 3 treatments on my lower legs and removed 60-70%. Whatever is left is so sparse and fine that I only shave once every 1.5-2 weeks and it doesn’t bother me at all.