There are a bunch of different figures associated with this decision, such as new interest rate, old interest rate, cash flow of new property etc, but I'm having a hard time getting my mind around how to analyze the decision mathematically.  

Every individual contract is different.

My goal right now is show them a few different options and the financials.

That would be different than say a place that someone famous lived in for some time.

This is a pretty critical difference.  

(So therefore we wouldn’t have to pass on the cost of the repair to him ie. the tenant).Now, several months later, I contacted the contractor to ask if he would be to provide a price estimate for a different job at our house.

There are Different ways of structuring lease options.

It , OF COURSE, also DEPENDS on your location and what you could actually get zoned up to.Are the properties around your building a different zoning classification than yours?

Keep in mind we are a "Mega PM", big staff big unit count, so it's a lot different then the Ma & Pa, but the principles can apply.

I would probably start with something different for your first property.