Most owners ask for one or two monthly rents as deposit. The deposit depends on the rental period, the tenant (number of tenants etc.) and the apartment. The security deposit ensures the owner against defaults by the tenant.
On the Crocodilian website, it always says that the deposit is fixed by arrangement with the property owner. It is always important to speak to the owner in person regarding the deposit. Only a few owners or their managers have a strict policy regarding the deposit (e.g. two monthly rents) so we can only tell you in these cases wjhat the security deposit is. The deposit is always due when you have concluded the rental agreement with the owner. It is payable by bank transfer to the account of the owner.
The security deposit is normally due immediately after that rental agreement has been concluded.
Please note, that the tenant has to pay banking fees (if there should be any). Owners cannot accept credit card payments. Most owners don't accept Paypal payment either.
Tenants are legally not allowed to withhold the rent and set it off against the last month's rent.
In the Crocodilian contract, the owner fills in the date by which he will have refunded the deposit to the account of the tenant. Unless there are any damages caused by the tenant or damages caused by the tenant because he or she has not carried out his or her duties - e.g. reporting defects or deficiencies (such as: water, mould or spots on the ceiling, caused by water coming from the flat above etc.) to the owner.
Please also note that you have to report damages, even if you are not responsible for them - e.g. if the washing machine does not work anymore. For the owner, if it easier to solve the problem when you are still staying there, It is worse when he notices after you have left and the new tenant is due to arrive, expecting a flat with a fully-functioning washing machine. It will also be easier for you to tell the owner in detail what has happened.
Do note, costs for final cleaning are normally also deducted from the deposit. Please note that if there are problems between owners and tenants - most often cleaning or cleanliness of the apartment is the reason. As a tenant, you do not just have to pay for final cleaning once - you are obligated to keep the apartment clean and tidy during the whole rental period. Please also read duties of the tenant when renting a furnished apartment.