While real estate can provide higher returns, it is subject to market fluctuations and requires active management.

I also figured that I would include in the lease that the rental price will be reevaluated every X months in case the utilities fluctuate dramatically.  

@Jeff Petsche there’s a federal base in Lawton which people come and go that increases vacancy rates to fluctuate.

I would say these area is the classic hotspot that doesn't fluctuate much because of tech economy.however if the O/P wants to invest in silicon valley area....I would say back in the 90s, "most" techie able to afford home in area like mountain view, palo alto.

Businesses come and go in any industry, and cities fluctuate with them.

If you have to choose between paying more to the lender each month or spending the money, then the 4% return is much better than 0%.The fluctuation in the value of the property has nothing to do with paying your loan earlier.If you keep the money and don’t give it to the bank (lender), you can get over bad times much easier.

The currency can fluctuate greatly affecting the value of a property. 

.- 1st Method: Focus on BRRRR on properties East of the 125 highway in regions such as Spring Valley, El Cajon, & La Mesa as these are moderately well priced in the SD area, have room for market growth (&loss, be cautious) as these inland regions fluctuate more than the coastal SD regions, and finally the amount of Duplexes & multi-family homes are more prevalent in these areas of SD. - 2nd Method: Riskier and heavily focused on Marketing to Condo Owners for Condo flips in Downtown San Diego.

I know midland has historically had a shortage of housing due to the oil and suffers from that cyclical economic issue do to oil price fluctuation but I know quite a few investors out there that make the buy and holds work.

Make sure concept is big enough to have FFC's ( fixed food contracts ) where food cost stays the same for product regardless of market fluctuations.