Collecting/Paying rent

[Nathan Galvan]

Hello, I am looking to purchase a duplex with my fiancé sometime next June. This will be my first property and I plan on renting the other unit out. I am a BEGINNER to all of this. When it's time to pay the mortgage every month, let's say the 1st of the month. Do I tell the tenant to send me the money on the 29th or 30th or the previous month? Or do I say the rent is due on the 1st of the month (I pay the whole rent and then put the money they give me back into my account)? Any suggestions? 

Thank you!