Can I make a contract, send it by email to my clients, have them electronically sign and then return the contract with payment?

#1 You can send the Form to the client/s by following this user guide

user guide:  -How-to-Share-Form-using-Email-Link

#2 The E-signature can be added to the form

link: http://widgets.jotform.com/widget/signature

#3 Add Payment Tool to the form

user guide: -Setting-Up-Your-First-Order-Form

Hope this help. Let us know if you have further question.

Thanks.