Perhaps hire a property manager to handle the phone calls and factor in the (depreciable) window, kitchen, HVAC costs?

We live in a low cost of living college town.

I'm wondering what is the current average cost, and seeking recommendations/advice.Ty 

You'll want to consider full costs upfront and an architect + contractor team is helpful in that process.

Why not buy it with private money, borrow enough for the purchase/repairs/carrying costs, and then refinance once the repairs are done?

You should also set aside money as a reserve for vacancies, turnover costs, bad renters, or capital expenditures (roof, flooring, and other big expenses).

I realize the cost may fluctuate as time goes by. 

That'll require you to determine how much the rehab will cost and pay that up front.

There was a relatively low cost to purchase and rehad the property.

I designed a 2 bed 1 bath stacked triplex that fits on a 30' wide lot with 3' side yards and we can build it for $174 a sq ft hard cost. we do them where the land is 10% of after repaired asset value which in our market is 50k approx. we study multifamily trends and stay with it.