CUSTOM SCHOOL WEBSITE SCRIPT PHP UPLOADS

Hey i am looking for someone that can write a script for me that will allow users to download 5 files off my website for every 1 file they upload. This is for a school website and it doesn't have to be complex. It can be anonymously done to where people wouldn't require a username or password. I would like to be able to restrict file types and file sizes also. I have some other scripts i found that relate to it so they can be used as a foundation if needed. I will add $15 to final value for installation of script. Thanks