I don’t think $30/hr is enough to cover the liability involved unless you have an insurance policy. An oops on a door panel or sill plate could equal several hours of work for free.Well, that's definitely an unfair blanket statement.
for the OP: $50-$100 per hour is WAY too much money for someone with no overhead. That is a "shop" rate. I charge about $30/hr for remote services. That includes me, a truck, and some tools. Obviously, it is hard to bring a fab shop to someones driveway. So, this is not something that fabricators commonly do.