Renting An Apartment-questions

I am renting a vacant apartment I have. I have a few questions. 1: When showing the apartment that I have for rent, should I give all perspective tenants an application? 2: Do I charge perspective tenants for the credit/criminal check I will run on them, or do I pay for it? 3: What happens if 3 perspective tenants are interested in the apartment. Do I collect the money it will cost me to run the credit/criminal check from each of them, run the first check, and if I like the results, do not run the credit/criminal check for the other 2 perspective tenants and mail the money back to them? 4: For the month’s rent and security in the form of a bank check or money order, and not a personal check? 5: What documents do I collect; Do I get w-2's, etc.?