Our economies, financial instruments, accounting, market manipulation, crony capitalism, derivates, currency printing and delinking from gold standard leave our economy extremely complicated and fragile compared to 1929 when things were not as complicated.

While they do seem low to him I do think it is important for you to explain to him your math and why/how you have derived to those numbers.

I won’t bore you with the math to derive correlations, but I will explain a bit on how to interpret them.

@Wade KulesaI believe Dave Ramsey's 10 year number is derived from the common real estate cycle, as 10 years is the time to complete a real estate cycle. 

From a mortgage appraiser of 14 years,If appraised for the bank, who typically go with FNMA Guidelines, the bank will not secure the property according to a value derived through the Income Approach to value, only the Sales Comparison Approach to value.

First off, the service in question and any derivative of this service, is a fringe service.

If it is multi family, the value is generally derived based on the rents, which is different than a single family.

The shorter tenor is easier for the lender to hedge the interest rate risk when it's providing the borrower a fixed rate loan (that's not done through a derivative).