Whether or not you ask your guests for a deposit is up to you: there are no legal rules for it.
Generally, a deposit is meant to cover minor damages, such as broken crockery or other household mishaps. Officially, you must present an inventory list to your guest for signature upon arrival, which will be checked after the rental period ends.

A helping hand : In 'normal' long-term rentals, the guest often has to pay 1 month's deposit. That means: 1/12 of the rental sum. So relatively small amounts, covering relatively small damages. Larger damages, i.e. larger than 1/12 of the rent, have to be obtained via citation and possible legal action.

It is customary to refund the deposit to your guests within two weeks of departure.