Specifically:value = rent / 0.01 (estimated via the 1% rule)NOI = 12 * rent * 0.5 (estimated via the 50% rule)cap rate = NOI / value = (12 * rent * 0.5) / (rent / 0.01) = 12 * 0.5 / (1 / 0.01) = 6 * 0.01 = 0.06In other words, combining the 1% rule and the 50% rule is the mathematically the same as assuming a 6% cap rate for residential.

As I was poking around at the relationships between jobs and potential predictors of job losses, I started looking at a mathematical representation of something less quantitative, that we are all familiar with.

It's mathematically impossible for prices to go up every year. 

Mathematically challenged?

I'm very mathematically analytical and have already made some simple spreadsheets to track my cost per lead/client that I plan on using over a 3-6 month period.

I still don't understand why you're still so insistent on the debt thing -- your comment "less debt enables you to help others" really doesn't resonate with me (nor does it make mathematical sense).If I have a $10M net-worth with $1M in debt and you have a $1000 net worth with no debt, who is in a better position to help people?

That's why I never trust website estimates, they just have a mathematical formula that spits out random numbers, it generates almost the same value when you have a 200k interior and 30k interior.

sometimes its just nice to own a trophy property which basically describes the better areas of SD.of course you can refi till you die and use all those mathematics that of course on paper make sense.but what if U sell it try to buy in a market that gives you a little more return on paper ( which is generally low B to C class) and now your stuck in an asset that's tough to manage and can go without rent fairly often because the tenants are NOT SD tenants .   

C properties trade in the 10-15% range typically, though you need to run sales comp in your immediate area to validate.I've heard of the 1% Rule (get 1% of purchase price per month in rents) so how are the 1% & 2% rules used and where can I find a list of these mathematical guides or rules of thumb & how to use them?

From a purely financial/mathematical point of view, you should invest in real estate rather than pay off debt if the return on your investment is higher than the interest rate on your debt.