How best to serve audiofiles?

I have a database of small mp3 files (1-3MB) that I am going to rent to my customers. It's going to be like a monthly fee to get access to the whole data I would host.
Now I am looking to find the best way to do it, knowing that I would like the process to be easy for my clients like 'register/pay + get access + use database'.
How to make the process secure and easy to handle? Have you seen similar websites?

Any advice appreciated!
Jean

Maybe my question was not clear and i am sorry about that. Actually I wanted to know what kind of architecture should be created in order to secure the whole process? Thank you.