Some go by the SQ FT to estimate but the age of mechanicals can swing the budget

Strategy is to continue to using the BRRR method, but I am doing it using my VA benefits which allow me to purchase for zero down no PMI.  

Also I'd like to add square footage to house by finishing attic as my space/bedroom so the 4th bedroom can be rented aswell.

No one has more "skin in the game" than a PMC as they have to deal with the property every day until an owner sells or fires them.Also recommend finding your own Inspector and not one referred by an agent.

I know that NY is more tenant-friendly and that the rent payments are made directly by "Arbor" and "DSS". 

I personally have 12-doors there and focused on the BRRRR method when I was building my portfolio.

I came across a deal and the owner wants to sell by owner only.

What do you mean by "you don't want to engage in interest"?

It will allow me to purchase a larger deal by having access to heloc and pay it down within a year 3k per month from combined cashflows from other rentals. 

Or alderman allowing case by case currently city wide but the regulations would make it a right of property owners without alderman approval needed?