Let's say, all missing accessories in 2015 would cost $150.

The income on the listing says they are getting $1,100  for the accessory dwelling unit so I am unsure how your expected income is $2,200?

Friends in Ithaca recently added an accessory dwelling unit when reconstructing the garage at their SFR in Ithaca and the process has taken well over a year navigating the city bureaucracy - with a couple of construction starts and stops because neighbors complained (spuriously) to the code office. 

It also allows the urbanhouse, detached accessory dwelling unit, duplex, and tandem house building forms."

. :)   plus to be fair I have coveted that parcel for years I tried to buy it pre GFC but market crashed and I was not in a position for a 5 million dollar deal in 07 08 as I was chasing down defaulted borrowers left and right  LOL.. but this year.. we took it down..

That will help narrow down what type of accessorial charges you can have. 

They are beautiful luxury homes with the coveted garages, which in this area are usually rejected by the community.  

I actually just applied for a "tourist home accessory use permit" via the website. 

I am currently waiting on sellers short sale approval to start on a Flip and have just wrote an offer on a ADU ( Accessory Dwelling Unit) property here that I will BRRR.

You can learn and team w/experienced folks in a more active pursuit or if limited on knowledge, time and significant dollars you could diversify into several value add apartment syndications that are in markets you covet.