BP has various tools to help you analyze your deals (rentals, flips, wholesale, etc). : https://www.biggerpockets.com/investment-calculators7.

In The Book on Rental Property Investing, Turner suggests analyzing 2 deals a day.

I don't think that them having a key to the property is a big deal.

Any advice for finding / approaching owners for off market deals? 

BP is good at filtering out the fake lenders.. one little post and you get to have the assurance your dealing with a real and reputable lender.

Prices in Columbus are still low enough to find 1% rule deals and there's a ton of appreciation happening in this market as well.

Got it at a really good deal.

I don't think it's a deal killer.

Well, the reasons given generally fall into two categories - either tax benefits through an “installment” sale or obtaining an interest rate on their capital greater than what banks are paying.In my 45+ years doing real estate deals, I’ve found maybe once that the tax argument was considered by a seller; further the “greater than bank rate” argument is completely irrelevant because - the proceeds of a property sale were never going into a bank account, at least not most of the proceeds.

Quote from @James McGovern: Do this often and you will develop a reputation for being deceptive and hard to deal with and unrealistic.