Although, I am moving on and not dwelling on what could have been, I think it is fun to hear others stories of "dang..I should have done that."

Otherwise the contractor is acting as a lender7) Our invoices are due on receipt, late on day 11 (with penalties and fees), and we file a lien on day 16.

Assume liability and cure at their costIT IS NOT appropriate for you to fix it and send them an invoice after the fact.

I have done what I can to automate things- invoices go out automatically each month and mortgages get paid automatically as well, and my time spent is extremely variable since we don't hire much out- we do the maintenance, cleaning, snow, lawns, leasing, etc.  

This is specifically Ohio law. Best to stay on the safe side of the law wherever you are  though!http://watsoninvested.com/wholesaling/

When I recieved the bill a week later, the invoice had the name of the company I specifically said not to use again. 

Seems there only wanting to invoice. 

You will need to prove a) the condition of the property before the tenants moved in b) the expense associated with repairing the damage (PAID invoices from contractors) and c) that none of the work constitutes an upgrade from the condition of the home prior to their lease.

If your JV agreement says "marketing" should mail 2,000 postcards / letters per month, make sure you get a copy of the Direct Mail invoices for evidence.

I can only offer obvious advice like taking photos and getting an invoice from the new GC which will be evidence of what work is still required.