The market volatility has been picking up, uncertainty on the political arena is concerning, plus the fact that the housing market in Phoenix has gone up to pre-recession levels.

There is some volatility for sure.

Some hesitations:1) Stock market itself is volatile.

Less volatile, not a ton of a appreciation, but more likely to have positive cash flow.

So the choice inside of retirement accounts is "do I invest in securities and get say 8-12 percent with a roller-coaster at times, or real estate where I can get 12-15% with very little volatility"?

Scenario A (typical) - $500k duplex-$125k down-$375k mortgage at 4.6%Scenario B (modular financing) - $500k duplex-$125k down-$260k mortgage at 4.6%-$75k HELOC on primary residence-$40k loan against 401(k) (technically this would be $165k down, but you get the point)In scenario A, paying off the mortgage quickly makes zero improvement on cashflow until you pay it off completely, or refinance, and there's no point in that if your rate is locked in lower than current(or future) market rates.Scenario B could involve higher interest rates on the HELOC and the 401k loan, but you have multiple, simple, easy options for increasing your cashflow, and then you don't end up playing as much in the overpriced, volatile stock market.

MFHs may do the trick even faster and provide many other pros including less volatility on the ability to service  debt, etc.  

The industry is volatile and unpredictable, I count myself lucky to have made it this far, and don’t want to rely on this income in the future.

For the first three options you want something with low volatility that will beat inflation, so TIPS or a money market.

The principal is secure and less volatile than other common retirement assets.