Hosting Billing Software

Hey, I'm looking for a high quality hosting management software. I run a hosting company with a few clients, but I need something that is unlimited. I need to have domain name renewal dates, and then hosting renewal dates stored, I need it to generate emails automatically and allow my clients to log in and pay by paypal or cheque or Bank Transfer. This needs to work with PHP and MySQL It needs to be quite simple. I only have a small budget of $50 to pay for this, as I can rent some software for about $7 a month.