Seller Finance Questions - Seeking Tech Advise

[Sam Borgia]

Hello all .. 

I have a deal that is going to be seller financed. I, as the buyer, am seeking advise or tools on reporting/tracking/record keeping software or websites. 

The Seller is non-tech-savy and "old-school". I am seeking a system or company that can be useful in reporting and tracking payments for the mortgage(for mine and the seller sake)... similar to traditional online banking that most of us are now use to.

It would be a challenge and inconvenient for the Seller to re-amortize and track all the payments and additional principal payments... not to mention the chance of human error.

Any advise from anyone or guidance on a resource? a software? a company?

Advise is much appreciated! Thank you very much!

-Sam