Additionally, I've yet to find a person who can "paper napkin" an investment with a HP12c or HP10B faster than someone with financial modeling experience.

put it on a napkin.

I take it you're not a proponent of the write-the-offer-on-a-napkin method?

These are all great ways to get a quick back-of-the-napkin estimate which is just what I was looking for.

Net result of a back-of-the-napkin calculation:$5,700 pro-forma$2,850 collected$2,736 (lower mortgage payment)------------------$114 cash-flow$13 per door cash-flow per month.88% cash-on-cash return at a 25% down mortgage------------------REAL net result:  my checking accounting has a better cash-on-cash return that .88% so you'd better be in it for building equity :-)

for me its being able to look at a deal on the back of a napkin and see if it merits more work .. like in 60 to 120 seconds.you get a feel for the macro stuff.. you should learn that skill so you can wade through the morass .. 

@Tegan Lehman you can write a legally binding contract on the back of a napkin.

The back-of-the-napkin math is that for every 1% interest rates rise, a buyer loses roughly 10% of their purchasing power. 

Now, if you are purchasing a SFR this doesn't really mean anything as properties are not valued based on cap rate, but you many use it as a back of the napkin way to figure out whether you will cash flow the property.

These are all things you can back-of-the-napkin model on a spreadsheet.