Internal PM/mail system like on freelancer.
You click a PM button and a window will open like the one here - then you can PM/mail back and forth with the selected user. Also there should be an inbox like the one on top of this page where you can see/edit sent and received messages.
You make this on your own server and I will test it there.
So basicly you need to create a simple login, 2 users and the PM/mail system.
Escrow: None! You do the job and you get paid.
11 freelance font une offre moyenne de $37 pour ce travail
I can get this done easily and for a low cost!! It's unlikely you will find a bidder lower than me as this is quite a complex task however I am experienced and can get it done.