What you can learn from my loss of a year's worth of work:Use your own judgment on the interest rate sensitivity.Figure out how much  NOI drops per 1% interest rate increase.Add 1 to the cap rate  per 1% interest rate increase.Then its pretty simple math to see how it goes upside down.My house is warm. 

Would need to be a very high priced zip code for the math to work out here.

The math didn't work at $250K, but it works at $222K.

I have considered the math and the concepts behind them. 

I am not buying it, I think how we do our math is totally different. 

Its a simple matter of the math.

and the permitting process might be cumbersome. but similar to the roof, get some quotes and do the math if you want.

But I'm hopeful that it's one leg of the stool for me that kicks in some business, and while it's not great math, I'm glad that I have already had the cost covered by transactions from leads.

The other option I would consider is regional credit unions that hold onto mortgages/loans and don't sell them to the secondary market - they are "portfolio lenders" and have the ability to be more flexible with their terms.

Obviously you'll want to check the math on all of this before pulling the trigger.