Admins can let users pay with a deposit for all shop products or only a part of them. In the first case, you have to activate the “Enable deposit” option, in YIT Plugins -> Deposits and Down Payments.
At the same time, set the amount requested with the “Deposit Amount” option.
Now users will be free to pay the complete order immediately, or pay with a deposit, as showed in the following image.
On the contrary, if you want to force users to pay a deposit, activate the “Force deposit” option you can find in YIT Plugins -> Deposists and Deposits Payements.
In this case, when users add a product to their cart, they will have to pay the amount of the deposit, and not the complete price of the product.