When you add a service agreement to a customer, you'll see the options to either 'Save now' or 'Save & send.' If you choose to save now, your customer won't see anything yet. If you choose 'Save & send', your customer will receive an email, prompting them them to view their agreement, and pay for it if they have any payment outstanding.
The can enter their payment information, as well as select the billing cycle that they would like to pay if you offer your customers multiple options.
If they will be paying on a recurring basis, they will be asked to save & store their card information by creating a Housecall Client Portal account. With this account, they can view the terms of their agreement, see their billing schedule, and update their card information.