The CF is only playing catchup to the cost to you of the property. 

On your tax return you would report the proceeds, subtract costs and proceeds paid to seller, then the remaining profit would be your flat fee.

He's changing the terms of the agreement, and you can choose to accept it or reject it.I don't think it's fair to pass this cost onto the tenant just because you are unwilling to stand up to the contractor.

That will increase your material costs for the job and is the contractor paying for the material in their bid or are you paying for it and paying them a labor cost.

Yes and a few bookings on Airbnb cost your ranking on Vrbo.

We know what the cost is to pay for some work and determine if we do some ourselves, is the time vs money a route to go. 

Over estimate the costs and not need them?

Naturally, they are your competition and the daily rates need to be taken into account.

Low cost, possibly yes, but also possibly very time consuming and that has a cost.  

Here is an example of what it costs you to avoid professional advice.