You can set a note to appear on the bottom of all of your estimates. This is useful because you will not need to explain the terms of the estimate to the customer each time an estimate is created as it will be at the bottom of the page. In order to create or edit this message, open your system settings. From the 'Estimates' section, click into 'Setup estimate note'.
You will see a page with a box. Click in the box and type the message you would like to appear at the bottom of all estimates sent to customers, then click 'Save'.