"Add Additional Fields" option on form front end

Currently using MODX Revolution 2.1.3-pl

I have a form that will eventually be used to send vehicle rental inquiries. I have nine fields that pertain to information about the vehicle (vehicle type, accessories, pick up date, etc). What I would like to do is have an "add another vehicle" option that duplicates these fields. So the user can enter in separate information for different vehicles if they need more that one. Being able to duplicate them an unlimited number of times would be ideal, but I would at least like to duplicate them five times.

Is there a known way to do this? If I need to, I can share my code, though at the moment it's just a standard Formit setup with drop downs and a text area making up the field set I would like to duplicate.

I'm not quite sure where to get started with this. I've found some methods that may work with stand alone forms, but I'm not sure how to integrate them to work with Formit. Especially when it comes to sending the email.

I appreciate any help.