This is literally one of the most awful ideas I have ever read on this site. Aside from the fact that even if you magically were good enough to soldier the wiring together 2 "gaming" PCs of any decent level would eventually overwhelm that PSU under heavy load burning it out. Theres a number of other bad things that can/will happen.
As USAF said, if you can't afford a second PSU you can't afford a second PC.