Also, be careful on any of these jobs that you get paid.
A GC on a Panera Bread store called my boss late one night, saying they had a health inspector's preliminary inspection & were told they needed extra lighting in an area. Said the process of a change or add on with the EC doing the jb was too slow, they needed a light that night. Boss sent me, I installed & gave EC the bill. He had already assured the boss their HQ would pay upon receipt. Never got paid. Boss called several times, was told they needed another copy of billing & our W9. Both were faxed, then they said we should send proof of insurance. Their HQ was out of state, BTW. Boss put a collection agency on it but they went out of business when Katrina hit New Orleans. Boss wrote it off. If I get a similar call, I will get a credit card from the GC first.
Another case, same boss. Apt complex called from next city over. needed an emergency night repair. Went over & fixed things up, gave maintenance man the bill. He assured me office mgr would send check next day. We eventually got paid, after 3 months or so. Turned out they had stiffed every electrician & plumber in Raleigh. We had to call dozens of times before getting paid. Beware the night call from a place who should already have someone regular. I will now demand payment in advance for such a service call.