6-unit property, great cap rate...what am I missing??

[Shawn Hershberger]

My partner and I are in negotiation for a 6-unit property in NE Ohio, below are details: 

• 4 rented, 2 vacant / average rent $735 (4 rented units $720, 2 vacant $775)
  • Owner pays water, sewer, trash
• 2 br, 1.5 bath, roughly 900 sf
• Garage with door + extra parking area
• Roof in good shape, air and furnace in good shape
• Realistic gross all units filled: monthly $4,400 / yearly $53,000
• We walked through both vacant units, very clean and basic. Could probably add $500-1,000 into each unit for cosmetics, but not necessary, ready to rent 
• We are discussing purchase price between $370,000-$385,000. Seller may be interested in seller financing, but hasn't decided yet. 
• With numbers above, cap rate is 8.9%. 

Seems like a great deal with very little downside. Would love some others thoughts. Am I missing something???

I've done a number of wholesale deals, never multifamily. I own 6 rentals but those were purchase almost 9 years ago.