If this is a bad deal because of $1,500/yr in interest run away and have your family sell the property. 

He can just put a mechanic's lien on your property and he will get paid when you sell.

(Luckily 99% is digital now so I can “help her” sign.)  

That's not enough information for anyone to give you any relevant advice.Does your neighbor want to sell?

There will be some customary fees that hit seller side, but this is may vary state by state.On both buy and sell, you will have things like wire fees, maybe underwriting fee, etc, but these tend to be minimal.Holding costs: HOA, if you have one.  

Hey,If "building class designation" is the same as zoning, then this seems like it can definitely be appraised as a two family, with both the legal and actual designation as a two family.Depending where in NYC, that may not help your valuation, as primary residences sometimes sell for more than investment properties, so check that out before challenging the appraisal and definitely before paying for another one.Double check all this with your lender/broker as well.Best of luck!

Stuff that is good to look into, it does cost a good amount to pay each month, but there are people who want to sell today and need a quick offer.  

How do you PAY back your contractor, did you take out a construction loan and repay them once the property sells or you refi?

The typical clients that seek out cost segregation studies include:Real estate companies that buy and sell multiple properties each year.Individuals with a portfolio containing investment properties including apartment buildings, multi-family homes and even single residences.Franchise owners with properties that are similar to one another such as assisted living facilities, storage facilities and golf courses.Business owners of hotels, food facilities, shopping centers, restaurants or manufacturing plants.It depends on the type of property, but generally 15-45% of the building’s costs can be classified into assets with a shorter life.

I would recommend flying out there, getting to know the area on a detailed level  and talking to local investors (someone not trying to sell you anything).