IMO.....if you kept it as a rental, your “cash invested” (your numerator) would be the cash you’d walk away with if you sold it now, after taxes.

Have them do a quick walk-thru of the properties you're considering and give you a ball park estimate. 

Here are some general details:- house is in West Hartford in a great location within walking distance of Blue Back Square- it is a duplex, but a little funky.

Purchase price: $140,000 Cash invested: $28,000 Duplex is located within walking distance of KU, main shopping venues, and a good elementary school.These 650 sq' units come with 2 bedrooms and a full bath, a stacked washer/dryer, and a big backyard.

That will refurbish provide a budget top.Ask any mobile home refurbish contractor to walk the home with you to define scope of work together and get a detailed estimate for the renovation.

Okay, maybe I was assuming a bit with the walking around inside, will email the auctioneer to verify. 

You need someone local.Even if someone like myself walked through a unit and gave you a tight number, it would be worthless because I don't know what subs/materials/etc go for in your area.

For example, say your estimated value of 140K is correct, you could possibly walk away with 50K in a cash out refinance after renovations, and 25% down payment.

Ironically, I would walk away with what I put in - $150k.I would like to buy a SFH or preferably a duplex where the monthly cash flow could be about $150 - $200.

Not saying not to do it but it’s walking a fine line.In several states including Maryland it’s considered predatory approaching borrowers who are in pre foreclosure / behind on payments and the fines are HUGE.I always go by the “how would this look on the front page of the New York Times” with business.