Not a bad idea at all providing you have the patience to do it. I've done it a few times as a favor and nothing pisses me off more than going over the very basic.
Good fences make good neighbors. A couple ideas to think about is a smaller fee as a introducing offer. To avoid running around for small money, just charge more. Maybe something like a 2 hour minimum (at $50/hour). Or charge them on a sliding scale; i.e.: the more they annoy you, the more you charge
