My emphasis on could.

There is nothing mechanically wrong with the furnace.

Anything above four units requires 25% down, shorter loan terms (typically) and more emphasis on the property and the experience of the buyer in terms of real estate investing.

All major mechanicals were also updated.

I got a higher end freeze-proof faucet that has an internal drain mechanism to relieve pressure if a hose is left connected, but I would bet he isnt going to leave a hose connected in the winter again. 

Key stipulations to keep in mind would be disclosures (lead based paint, structural/mechanical/public safety, insurance claims history) and which items do and do not transfer with sale.

We replaced all mechanicals, framing, drywall, etc!

It's not absolute just one mechanism among many with due diligence and a purchase and sale contract to try and keep the seller honest. 

At the end of the term of the lease, if there is more damages than the security deposit amount, you can still bill for the extra as long as it's reasonable and stemming from their use and not age of the property/condition of the mechanical systems. 

There are other IRA funding mechanisms for REI, that Others can note.4.