I'm not trying to be cruel by any means either.
I can just tell that you're woefully under prepared to actually charge anyone anything for your work.
You've got to consider it from the side of whoever it is you'll be recording. Why would they pay any money to sing in your closet?? It's almost insulting to them to even suggest it. And while an Mbox is awesome for the home recording hobbyist, it's pretty naive to think that anyone would walk into your bedroom, look at your closet, look at the MBox and be impressed and inspired. And if they actually recognized the microphone for what it was...they'd probably just wonder why the hell you spent so much.
I would suggest that you start out by offering your services for free. Expecting no payment. If they WANT to pay you. Then take their payment but morals would suggest you only accept payment if they're satisfied with your work. Use the jobs you do get (regardless of payment) to put in time practicing and building a "portfolio" of sorts. Then later on when a potential client wants to work with you, you can show them what you've done in the past.
And I'll caveat this whole thing by saying how absolutely ridiculously difficult it would be to start this way and make a significant amount of money.
Because of the nature of what you're trying to do (at least what I suspect you're trying to do) I would propose that it would be completely immoral of you to take a single cent from anyone unless they had heard what you've done with their recording and were 100% satisfied.