I take the deposit immediately.  Either by credit card (pay pal, VRBO/HomeAway, or I take it on my iPad with a program called Square - its free to get it but they charge 3% so I prefer not to unless the renter is going to pay the balance by check) or  they have 5 days to get me a check by mail.   If they cancel more than 30 days prior I do refund 100%, of deposit, if less, they get it back if get another booking.  I do this because I've had guests re-rent with me when I've done this, they see me as being fair.  Its written in my contract.  I then collect my balance in full 15 days prior.  If it is not received, I contact them, and either they lose what they paid and the reservation or they pay by credit card and the 3% fee (also in my contract). They are actually always good about it because usually they just forgot and dont want to lose the reservation or their money.  Each market is different - see what others are doing, if they do payment in full 30 days in advance, do the same.