As an alternative, the judge would have considered any payed/invoiced repairs as evidence so if i would've gotten the repairs done and payed for them, he would have awarded me the costs.4.

You forgot to add, "and now that that's settled, here's my invoice." :) 

I have seen things structured as a consulting fee for "acquisition analysis" where there is an invoice for evaluating a deal for a flat fee.

@Jeffrey Nordin - regarding management, most of the PMs loved to spend my money, encouraged repairs that I wasn't even doing on my own house, because they marked up the invoices a lot, and that's how they made the majority of their money, even though you also pay a monthly % of rent fee. 

For an even bigger discount, get a cash back credit card and pay off your lowes/HD account with said credit card.The BIGGEST reason to get an account is invoice tracking.

I also encourage them to have an invoice ready as soon as possible upon completion as the second they are done and I am satisfied, I will cut them a check.

Since I already use QuickBooks for my accounting, I simply send them an invoice via QuickBooks that they can pay online...I can control which payment methods to accept on a per invoice basis.

If I have one receipt that covers multiple houses, I'll break it up by Class -- assigning the correct amount to the correct Class (house).If an invoice covers multiple trades, I'll break it up as much as reasonably possible, though I try not to go crazy (if a painter gives me a bid for two coats of paint, I won't break it up into two line items :). 

The houses were supposed to be rehabilitated, but in 6 months rent, I had 1,254 $ maintenance cost for one and 858 $ for the other without seeing any invoice.

I'll have to pull invoices to compare to what I have been paying, My concern is having a company behind the install.