One your host confirms the booking, you will be sent an email with a link to the payment page. You have 24 hours to make the payment, otherwise the booking will be automatically cancelled.
In the case of a Long Term rental (3 months or more), the first 3 months are charged up front. Subsequent months will be charged 1 month in advance.
If the host has requested a security deposit, the security deposit will be charged to your method of payment, however it will be refunded 48 hours after your check out date if there haven't been any claims by the host.