How do i let people pay in person?

I am not exactly sure if I understood your question correctly. Do you want to have payment field inside of your form, but you do not want to charge your users right away? If you just want to allow your users to order and you want to charge them later, in person, then you can use Purchase Order payment field. 

If I did not understood your question correctly, please explain in more details what you are trying to achieve.

Hope this will help. Let us know if you need further assistance.