Friday came around, so we emailed multiple people within the company that basically said "please send us a final detailed invoice within 2 business days, or we will send a check based on work completed and prices previously quoted."

Start by looking up rehabbed properties, checking tax records to see what they bought the project for (I still do this all the dang time).  

I always tell him to let me know how much it is or send me an invoice and I will pay it.

During my time there I invoiced $2,809 and with my 50% commission split, I am owed $1,404.

I've been extremely quick to get any paperwork my mortgage company needs including just recently a stamped letter from the IRS that says no one else is using my social, an registered copy of my divorce papers from 2005, TWO contract extensions because the underwriters are so dang slow.

Maybe I'm just too dang nice then.

yeah... i think he wants cash to make sure he does not have to report it. does he invoice you?

@Michael Dang posted a good summary of meetings here: https://www.biggerpockets.com/posts/3454735/

Deliver an updated invoice with the late fees showing that it is past due, but in parallel also 2. begin the eviction process, I wouldn't worry about leaving a note or going into the property unless you have cause (water leaks etc).  

Management companies may keep all, part of, or none of income associated with returned check fees, rental income for pets, lease violation fees, unpaid invoice fees, bill payment fees, or income from laundry or vending machines.When assessing a property management company, make sure to ask specific questions about their fee structure and the services included.