Trying to buy multiple properties from one owner

[Joe Fornasiero]

I'm house hacking my current home and found an off market deal with a seller who has a duplex and a home on one lot and another lot with two homes on it. These are all on the same street right next to each other. I'm trying to determine if I could still get FHA financing to purchase all of them at once or if I would need to do commercial financing? The owner will consider a land contract but wants a large amount down. There is one duplex and 3 houses in the deal.

Numbers:

Gross rents: $4,480/mo
Vac/Maint/Capex: $1,120
DTE/consumers (for duplex) and trash: $300/mo
Insurance: $300/mo
Taxes: $981/ mo. 
Minimum cashflow required: $500/mo. 
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Max mortgage amount- $1,280/mo

Offer would be around $250K with FHA 3.5% down financing (assuming it qualifies)
some of the units are below current market rents and I would also look at adding separate meters on the duplex.
Owner said she's had two appraisals one low and one high the average came out to $450K. Her husband passed away two years ago and she doesn't know how/want to manage them anymore. 

I just finished reading @Scott Trench's book and think this would be a great way to start growing my portfolio. 

Any insight on creative financing strategies would be appreciated!