@JeffSchwenk - I believe that is called an ""employee"". LOL!
In all seriousness, I have reviewed this request by customers in the past, and there is no easy way to do this. I am sure it could be done. What about using one of the document management integrated solutions like Acom? In theory, it has the ability to read electronic documents and input the information into invoice data entry. Of course, this means the invoices need to be in electronic format first (scanned) and then someone needs to review the data entry and post it.
Could they have that same third party enter all of the invoices into a spreadsheet that is formatted properly for importing in Sage 100 using VI? They could do the same with the payments. Or, they could have a spreadsheet that is imported into Manual Check Entry that includes the invoice information.