how can I create a form to collect money that will have a balance

 I am not sure if I understand your request clearly but, if you mean to collect money and calculate their balance that it's not possible on the form. But, you can integrate the form with Google Spreadsheet and modify that sheet so it can calculate the balance.

Please follow the instructions from the link below on how to integrate JotForm with Google Spreadsheet.

https://www.jotform.com/help/228-How-to-Integrate-Form-with-Google-Spreadsheet

Please let us know if you have any other question.