Pay as you fill out form / instant invoice?

I'd love input on how / if what we want to do is possible. 

We have a website for the real estate agents in our company.  It's an internal agent portal situation.  On this portal they fill out a work order to order a media shoot.  

Is it possible on that form to have a way for them to pick a service and pay immediately upon filling out the form?  Is that within the invoicing space or is this more of an e-commerce 'store' situation?  We want to streamline it all so we don't want to have to send invoices but pay upon filling out the form.  

Thanks for thoughts!