In addition to being soaked with dog pee, the deck is also very weather beaten and this stuff seems to really be helping.  

Any depreciation deductions you took on previous tax returns (or were allowed to take, weather you took the deductions or not) will have to be recaptured (included as income) before figuring the capital gains tax or tax exclusion.

We can only make educated guesses based on  historical norms.We are due for a recession at some point but its tough to forecast exactly when so why try?

Alternatively, a real-estate professional has given me some estimated numbers for taxes, for a revised IRR (which is lower).I also understand that forecasting exact expenditures + their timing is hard yet can impact the IRR's accuracy.

All four people were weathered investors. 

I'd tend to think the weather there typically doesn't make frequent power washings a thing?

(weather you double close or assign is up to you) the person that sold you the property, can't decide for you. 

But I know I'm perfectly happy to work on a flip over the winter so that I can have something to list to retail buyers when the weather warms.

. :)Good luck in this hot weather!  

Our weather hits all the extremes, I think most good quality people expect cent/heat & air.