Videomaker – Learn video production and editing, camera reviews › Forums › General › Video and Film Discussion › professional forms (contracts, receipts, etc) › Videomaker Mag has a book
Videomaker Mag has a book of forms for contracts etc. Or you can google that or ask a lawyer.
If you need a good looking receipt, quickly, and have Microsoft Excel, you’ll find a template for receipts in the template folder (depending on version) File>New>Templates on My Computer>Spreadsheet Solutions>Receipt
I think getting accounting software is a good idea too, it’s just that learning how to use that software takes awhile.