In addition, you need to know the current Legal Rents in the records of HCR (DHCR) for each apartment as they will be rents that you will most likely be stuck with and you will not have the ability to increase rents to cover Rehab or your investment.

Most of them are however I am "thinking" I may have a shot a negotiating additional money off if I can say to builder that I know they are not paying the realtor fee.  

However, when I design my own house in the future, I plan to accomplish this in addition to other green energy features.

203K is not affected the addition of units. 

Many lenders will charge additional rate increase if loan is under $150K.

I work for a home builder and get a generous discount on new homes...

At no additional charge. 

For all of the additional work involved, I'd be hesitant to do a STR deal at 10-15% but of course it depends on what your goals are for the property and for your finances. 

Additionally, It is noteworthy that the seller was a member of the HOA board at the time of obtaining this permit, raising questions about the legitimacy of the process.Though I am not currently residing in the apartment, I took the initiative to rectify the flooring issue in cooperation with the HOA, given the significant disturbance experienced by the current residents due to the subpar quality of the previous labor.Furthermore, short after I bought the unit, I discovered an assessment imposed on the condominium, which I was not informed about prior to purchasing the unit.

The longer you wait, the more likely mold starts to form and creates additional expenses and damage for your project.