Well, their are a couple forces at play for something like this.
The learning part I'm not too worried about, other than the learning curve of working with the people in this niche.
The DIYers around me seem to be more into doing it for the financial end, and not so much the reward of doing the project yourself. That being said, I would worry that if my fees were inexpensive, I'd be running all over town doing only this, and not making very much $, which is not my intent.
And I think the 2 hour minimum charge would force the customer to be conscious of the time, so an appointment wouldn't drag on unnecessarily.
The other thing at play here is opportunity cost. If I spend 5 hours doing this, how much could I have made if I'd spent that same time supervising a crew on an install, or selling a project to another client? Would I have made $250?
The more I write the less I like my idea........