Contracts between investor and buyer

[Gabriela Chavez]

Hello! Rookie here. If someone will please allow me to pick their brain that would be truly appreciated. As my partner and I are creating our Real Estate plan we keep stumbling upon this question "what are the basic contracts needed between the investor and buyer when executing an Assignment of Mortgage, wrap, rent to own? 

I know the SMA and Purchase & Sale agreement are the proper docs for seller. Could I get a confirmation on that as well. Thank you in advance!