It is entirely up to you if you wish to set a cleaning cost as part of your booking costs.
If you choose to set a fee, please make it clear in the house rules and on the Goform how you expect the vehicle to be returned.
If you do not set a fee, please also state how you wish the vehicle to be returned and if it is not to the agreed standard then you will be able to add a cleaning fine which will be taken from the security deposit.