The rental details will vary from person to person, so there is no "official" policy on what is normal.
You should plan something that you are comfortable with and then put yourself in the renter's shoes and try to find something that you would be ocmfortable with from that side. Win/WIn situations are always more satisfying for everyone.
Some of the answer depends on how soon the trip would be. If you have to make a reservation for a trip within 30 days- you better get full payment in advance or you'll be stuck with the holding account if paymert is not received.
If you have several months until the reservation date, you can be more flexible, if needed.
Good Luck!