In some states property managers are required to get their CPM (Certified Property Manager) or ARM (Accredited Residential Manager) certifications.

i know i need a certificate of occupancy but do i need a housing business license?

It's likely that the agent who owns this property can prove with a zoning certificate that it has 3 legal dwelling units, though it would ultimately be up to the buyer's due diligence to prove such. 

As the owner in NY of a rental property do I need to obtain a certificate of occupancy and a housing certificate if I’m hiring property management?

Depending on the audience, the certifications you have and the business classification of the fund you may or may not be able to advertise to specific groups.Michael

You should have received a certificate of sale, but I would wait to receive the deed before spending any money.  

I have heard that inspectors need a special certification to inspect that stuff.

As long as your credit is good (I think around 650), you can borrow money from P2P sites.4. secured Personal line of credit - if your credit is NOT so good, and you have some assets like Certificates of Deposit or stocks, talk to your banker about opening a SECURED personal line of credit.

If she used a pay site for her certificate, they may reject it. 

If the owner is deceased check the vitals statistics dept and request the death certificate.