Custom user management system. How much will you charge for this services? 

Basically, what I would like to do is crowdource tester management system. We will go get the clients, and match with testers that in our platform. 
Tester also can see their current and past testing project.
Tester can check overall payment, payment history and payment yet to be disburse. And Admin can give ratings to users based on their project. Imagine that this is kinda like freelancer.com but we dont want to have the supply portion, only demand.