Need insight on a rural duplex deal

[Gretchen P.]

I have a lead on two duplexes in a rural area, $60K total for both duplexes.  Rent in the area for 2/1 units is between $600-800/mo.  I am assuming $30K in repairs total. All in will be $90K, with conservative rental potential of $2400/mo (4 units x $600). I am assuming 15% vacancy, and will have the property managed. Taxes for both duplexes together are $640. 

The town is very small, 2500, with a junior college (enrollment 750), hospital and mining/quarry/oil/gas industry. Median household income is 72K, and the population has grown 15% since 2000, unemployment is around 5%. 

If you have invested in rural properties, what due diligence should I do besides the normal inspections, etc?