Depends on what you desire more, peace and quiet, or a bit of extra cash. Right now i need extra cash, so carrying out work is something i'm currently happy to do. I currently have someones pc, and they are happy for me to do x, y and z with it, pay me, and pay for any parts (there's no probelms with it, they just want it to be faster and have it for their kids to use, they have an old 775 celeron d in there atm, i can shove a dual core 775 i have somewhere at home from another job)
I have said im busy up until xmas and they just said to keep it aslong as i need it.