Is it legal to sell files that were uploaded by the users?

Question

Is it legal to operate a website that works like this:

1. User 1 registers, uploads some file, sets its price and description
2. User 2 buys the file, money goes to website's bank account
3. Site takes its cut, sends money to User 1

The main point of interest are copyright infringing files - obviously the site would remove bad files on first notice and try to prevent such files from being uploaded in the first place.

Answer 1

You have basically described the publishing industry. User 1 writes a book, sends it to the publisher ("uploads" it), User 2 wants a copy, pays the publisher (who gets the money, and takes a cut), then send money to User 1. There is the same concern over whether User 1 actually has the copyright in the book. With that concern addressed, it is completely legal.