Module to handle payment for development?

Ok, I've been thinking about a kind of bounty system and wondering if there is something like this for Drupal?

Basically, I want to be able to put up descriptions of jobs to be done with relative complexity (easy, hard, bleedin' hard!!, etc.) and an estimated time frame for said work (optional - as normal work days could get in the way).

With this description there should be some way for people to donate money to (put into escrow via card/PP/etc). This could possibly have a target amount to reach before work is even started (e.g. I won't work until the target of £20 is reached).

On completion of the job a binary demo is posted (for SW), the people who have donated determine whether that is work done for escrow, and the cash is then paid to my bank account.

So, is there something like already or can it be done using other modules?

Thanks,
Luke.