@Joanne Hanson My favorite source for a beginner is Every Landlord's Legal Guide by NOLO.

Looking for guidance or to be pointed in the right direction to figure out how hard of a task is it to convert a 2 family legally into a 3-4 family in Yonkers, NY.

All the other pieces are lined up (investors, sponsors, loan broker, legal, management). 

I can go the legal route to enforce their contract but I feel like involving lawyers is not worth it, it is not worth dealing with these types of people.

I have no problem drawing up a new lease in his name only but is there anything else I need to do to show legally that the old lease has been terminated or will the new one automatically supersede the old one? 

From there I eventually switched to just searching the county records for legal issues.  

A lot of forum members are very knowledgeable in their respective fields related to real estate investing, whether that is real estate sales, wholesaling, flipping, rentals, lending, self-directed IRA and Solo 401k investing, or tax and legal guidance.The site has quite a few tools that can be helpful for new members.

They simply didn't want the property anymore due to the extensive legal issues that came with it and their father's past.

I reviewed the lease and the first part states they will take immediate legal action for failure to pay rent.

Make sure you have legally binding contracts drawn up if you do invest with your boyfriend prior to getting married so both parties are protected.