How come he isn't paying the full amount?

Contractors, unless you have a working relationship with them, normally do not want you bouncing ideas off them.Understand what their hourly rate is, have a discussion with them that you are okay with paying them an hourly rate if they walk the property with you and provide you a scope of work along with an explanation of what you can/can't get away with in regards to improvements.ask them if you go with them, if they can credit you the amount that you paid.Once you develop a working relationship with a few contractors, you can bounce ideas off them and expect quality responses.I do not invest in New York.Best of luck. 

Later I find out from the tenant that the tenant pays their rent early and has already paid January’s rent.

Purchase price: $740,000 Cash invested: $1,300,000 Sale price: $3,850,000 I refer to this project as a new construction house hack, as I secured a primary residence construction loan for a two-family home.

OPIf you have a company with a Sales tax license.  

Purchase price: $185,000 Cash invested: $35,000 Sale price: $671,000This was our 3rd home.

Is the 11% equity from the appraisal over the sale price?

What about having to break even, or even feed the property every month $200 for those same 36 months, but at sale, could net a $75K-$100K profit?

I’m going to disagree with @Chris Seveney and say whether an assignee could force a sale directly would be a state law issue and heavily dependent upon the contract terms. 

What I usually see is that they start with the average $/sq.ft of the sales price in the area.