Remote work confirmation by non-bias party

[Dragan Jeremic]

Good day BP community, 

I have a few remote properties (both fix and flip as well as rental) and very often I am struggling in getting the non-bias review of the work done. Unfortunately, there are a lot of sweet talker contractors that persuade me that they have indeed: cleaned snow, mowed lawn, completed painting the house, removed garbage or any debris, or similar, but they do not send me the pictures as a proof.

Of course all of them ask money in advance, and even though I try to send payments only after the work is done, it's not always possible.

My question is, how do you fight those situations?
What are your solutions to get confirmation that the work is done, as the contractors say it is. 

Thank you all in advance for your thoughts and ideas
Dragan