Oooh, how mercenary of you.
I suppose if you and your clients figure out an agreeable price, if certain maps are worth that much to someone, it might cut down on the begging. Throwing money around, like it or not, does seem to cause things to happen, in almost all situations.
The only thing is that anyone paying for commissions (or anything) should understand that whatever deal or transaction happens here is between you and the other person; if a deal goes bad for any reason, VGMaps.com is not to be held responsible for any of that.
That being said, carry on.
EDIT: Now make sure you think this through. You will have to be prepared for some interesting scenarios. For example, what happens if someone wants to pay you for a huge job - and it's not particularly exciting for you, and maybe even technically challenging. And you start work on it, and it takes a long time. What if, before you are able to finish, someone else independently makes all of the maps and submits them, and they turn out to be comparable, equal, or, dare I say it, better (in the client's eyes) than the maps you are commissioned to do. If the client finds these other person's maps satisfactory, they won't want to pay you. (They also aren't obligated to pay the other person who fully mapped it, especially since maps have (as far as I know) always been submitted here with no expectation of payment.) What then? Your time has already been spent making some or most of the maps. And if they aren't fundamentally different to the ones already made, I wouldn't see any point to put them up. Would you be okay with such a scenario?
Even without that, there would have to be enough understanding between all parties involved. Does the requester pay first? What if the mapper is unable to finish or takes much longer than expected? Or does the requester pay at the end? What if they're jerks and decide not to? If it was merely an online purchase of an item that merely needs to be sent out, then paying first makes sense. But we're talking about something that can potentially take weeks, months, or even years. Unless you are able to make this your full-time job?
Maybe I'm overthinking this, but if you are serious about offering your mapping services through commission, I hope there aren't new problems that arise from this...