Ideal purchase price on this example multi-unit property?

[Mike C.]

Lets say we have a 6 unit property built in the late 80s with these specs:

2 bedrooms, 1.5 baths, single car garage, laundry hookups

$4500 total rent per month ($750ea, all utilities paid by tenants)
-$800 taxes
-$200 insurance
-$675 expenses(10%)
-$675 vacancies(10%)
---------
2170 monthly income(cash flow), if all units are rented
1645 monthly, if 1 unit is vacant
1120 monthly, if 2 units are vacant
595 monthly, if 3 units are vacant, lets hope it does not get worse than this

Property will be paid for with cash. No major issues with the property and nothing that needs immediate attention. Roof, windows, doors, garage doors, gas forced air furnaces, AC heat pumps, appliances(stove, dishwasher, fridge may have been replaced, but still dated), and toilets all original, so about 30 years old. Gas hot water tanks are not original, fairly newer, maybe within the past 10 years.

Lets assume the rent is good for the property and area. Lets also assume school district/job market is good and crime rate is low. 10-15 minute drive to cities/shopping/work. This property will not be located in a major metropolitan area.

Updating units slowly may be beneficial, however, only expect rent to increase 50-$150 range.

If there is another piece of information that is needed, let me know. If not, what would be a good/ideal buying price for such a property?