Quote: "Do you know if its possible to automate things. I.E. A customer purchases a product from my website paying me $30, I keep $5 and send the remainder to the person who created the software."
You can't automate the transfer of money, but you can provide 'landing pages' which depending on the payment result are called. You can therefore on the success page email the person that they have a sale, and then pay the person monthly.
Quote: "And also I need to provide secure download links too..."
Thats something for you to figure out. A simple solution would be to get an ASP/PHP script to make a folder with random letters and copy the download to it. Then provide the customer with this location. After a week or so you can safely delete the folder.