Require Contract at Checkout

[shopbrickify]

Does anyone know of a way, either natively or 3rd party app, to require that the customer sign a contract at checkout?  I would like to do this both online and in person using the Square POS app. Thanks.

[homeprogreen]

You can create an estimate in Square then they accept the estimate and you convert it to invoice to check out. Might have to choose an upgraded version of Square POS in order to get the estimate function