People will typically patch and repatch mechanical and shelter systems but most everyone will heroically defend a set standard. I've seen people patch together plumbing and electrical systems but they always find the resources to keep the toilet flushing and the TV working. Some people could seemingly eat dirt and live in a ditch as long as their video games worked. Everyone will defend those things that define 'civilized' for them.

The good news is that people who can make things work always have work. Bad news is that getting paid is always harder than finding people who want work done. People willing to pay substantial sums of money will have had the system patched many times so the jobs you get as the expert of last resort will be larger and more complicated than would otherwise be the case.

If you work these sorts of situations always get the cost of materials and living expenses covered up front before you start work. You can go a long time breaking even or with minimal profit. Losing money on a deal can be financially fatal.