Hi,
PHP expert here. A few questions:
Are you using any well-knows CMS systems or is it custom developed?
Are the payments currently stored in any way?
Are the payments calculated or manually entered by the admin?
While discussing the details I will change my bid accordinly.
After all questions have been clarified, I'm ready to start right away. We should be all done in 3 days tops.
Regards,
Bence