The development is nearing completion, and SFR units are already being leased before the Certificate of Occupancy (CO).

This is different than merely being a certificate holder and have appropriate insurance (builders risk and general liability). 

You need to a certificate that there is no mold as the tenants can easily go after compensation-a valid reason to refuse paying rent.

In connection with its duties, Qualified Intermediary shall be protected for acting or refraining from acting upon any written notice, request, consent, certificate, order, affidavit, letter, facsimile, email or other communication or document furnished to it under this Agreement and to have been signed or sent by Exchanger or any of its officers, attorneys, or other representatives, provided, however, that any instructions relating to disbursements of funds shall be subject to the provisions of Section 3.4 above and the Disbursement Instructions shall be signed by the taxpayer or submitted by the taxpayer online via the Software."

This house HAS A CURRENT lead safe certificate issued by the Toledo Health Department.

This is something I've been mulling over and I admit that I'm kind of curious to know how it all works (regulations, certifications, process) 

The units are already being leased before the Certificate of Occupancy (CO), and they come with one year of complimentary property management to maximize cash flow.

Do I need a business license or certificate of some kind to rent?

The operating agreement is more important than the certificate of organization/ state filed equivalent.

Either an in house maintenance person with HVAC certification or you have to hire out subs for the various jobs.You can always contact PM companies and ask them what they budget per unit for maintenanceGino