I am building a website that needs a form. Can I purchase a form from you and insert it into my website I am building?

I would suggest you to check on our templates page so you may find a template, clone and modify it, here is the link: https://www.jotform.com/form-templates/ 

Here's also a guide about it: How-to-use-the-form-templates

You may then embed the form into your website, here is a guide that will help you to decide which embed code you may use: Which-form-embed-code-should-I-use