My main question is how much value will a deck add to the appraised valuation is it a good return on investment.

For example I just did 3 decks for our properties and got grey select Trex in bulk pricing from the lumber yard.

I was nat able to make this months so I just pulled up the slide deck.  

I cannot speak as to whether anchor bolts were required at the time of construction of your garage but if I wanted to find out I would first start by asking structural engineer.Unless you are changing the garage in a way that would require a structural review during the permit process (for example: adding a roof deck), I think there is a near 0% chance this would get flagged as a code violation.

We hired out the new electrical service, wiring, drain drop,and stove pipe replacement, and did the new kitchenette, floor sanding, new deck, and paint ourselves.The Tiny Tipsy Cabin is currently rented on Airbnb with hundreds of reviews and a 4.8 star rating, and net income is about $3,000 a month before accounting for debt service.

New electrical service and wiring, new kitchenette, floors sanded, wood burning stove-pipe replaced, and new deck installed.

Looks to me like that may have been a porch or deck at one time, looks like the crack is along the top " course " and then goes down by the outside corner. you need to find out how it was built. to me it looks like the corner was a pier and where it is cracking along the top is the separation of the wood floor joists from the concrete block and that the block was put in later to fill in underneath. there probably was not a good footing put under that block because they had trouble digging ( working) under the existing floor system. put a level on the floor and see if the floor is out of level, just to make sure that it is not the foundation sinking, but i do not think it is.

A rooftop deck would also add about $100-125 a bedroom.

One famous insurance matter involved a second story deck that was added onto an older building some years ago.

Improvements will include interior/exterior painting, some minor plumbing, installing flooring, repairing wood stairs and deck, and possibly a wall removal to make into a studio.