It also is not easy to attach to the main building, we could attach it to the first floor if we remove the shower and go through the bathroom, but I think if we were to fix it up, it would have to be a seperate bedroom(not sure if that is legal), or more likely an office space.

It is true that this is a very expensive location, it's all custom work, there are two bathrooms and a kitchen, and it is retail. 

My tenant's upstairs bathroom sink was clogging, the previous owner helped me repair it, but man I feel so proud of myself...

Appraisals are based primarily on square footage, number of bedrooms & bathrooms, location, condition of the property, and school district.

I was just at Home Depot looking for grout (yay new bathroom!)

Check the whole bathroom.

They deliver property fully renovated: new roof, new pluming, floors, kitchen, bathrooms, paint job- all is done, but basic, of course.

Plumbing, electrical, water damage, bathroom fixtures, kitchens, furnace needs replacing, question on if it's a legal 2 u it or 3 (only 2 con Ed meters), everything needs fixing or updating.  

For instance, a second bathroom, even just a half bath goes a long way.

I use mls however, my comps are a 5-10 block radius plus sqft, beds, bathroom,  garage, and basement to determine value.