I used this method in college when subletting rooms to roommates.

I am wondering if these are both possibilities and which might be better, so IF I need to keep track of building costs that are specific to that area I know that going in and getting bids etc...1) Use the 'square foot method' - this square footage will be approximately 17% of the overall area of the home.

But, it's a time consuming and who knows how long before I can reep some benefits from this method.

They are often generated by agents doing CMAs, comparative market analysis, which is a method to compare properties to guestimate what the fair market value is.Fair market value is the value at which someone will buy the property within a reasonable time.

What would be the gain vs drawback of either method?

Then there was tree trimming and now there is front sod that HOA wants me to replace.

You certainly don't want to pay for income you plan to trim off:)If you decide to take on this deal, make sure to do a demand study for the sale of the homes before you proceed. 

Look up the BRRRR method---buy, rehab, rent, refinance, repeat.

"comparables" IS the method that's used for pricing single family homes.

Any help in deciphering the method to this madness would be much appreciated!