First deal, trying to verify my numbers

[Max McNally]

I'm looking into buying a multifamily property (6 units in Ohio). I've run the numbers a bunch of different ways, and they seem too good to be true almost, so I was wondering if someone could verify, especially multifamily owners in Lorain County, Ohio.

The property is three duplexes on two lots, asking price is $125k. They seem to be in good shape, but they are older buildings ~1900. The owner says they have newer roofs, newer heating, and are well maintained. They are section 8 approved, and fully rented. The owner claims to be collecting $680 - $720 per unit gross rent. Each unit is 3 beds 1 bath. Annual taxes are $2,945. 

Here's my breakdown, using the low end of the rent range ($680 per unit)

2% rule 

$4080/125k = .032% 

50% rule 

$4080/2 = $2040 

Property management (10%) = $1632 net per month

So $1632 per month cash on a ~ $31250 investment, or 62% per year

I did a separate breakdown using real tax numbers, 10% vacancy, 10% property management, 5% maintenance, and insurance, and I come out to over $2k a month net. 

Does this seem accurate? If it is, it seems like a no brainer to buy, right? I'm just wondering why no one has jumped on this deal yet. It's been for sale for almost a year now. Should I be worried about that? 

Also, since it's more than 4 units, I would need to put 25% down. Would be a good idea to offer to buy them seperately? 4 units now, and then the other two in six months or so? Would a bank allow that? Any thoughts on what I should offer for the properties? Thanks so much for your time!

Max