Lake Worth seems to be filled with small multi-families but I've heard it's hard to find/ keep good tenants due to the LW utility system which supposedly has unpredictable service outages and fluctuating costs. 

Odds are that a few weeks of random market fluctuations upwards to rate will be waaay less than a bunch of rate lock extension fees multiplied by 7 loan amounts.

I also plan on looking at how the markets I am looking at fluctuated in last real estate bubble, to find a market that is less prone to wide swings in price.  

How does that work when rates are variable and payments can fluctuate?

I found it interesting, because it expanded the portfolio on a regular basis, but the quality of rental could fluctuate greatly (depending on the capital acquired).Anyways, just tossing it out there.

You're offering up an asset that has a fluctuating and very unpredictable price with no income generation while the remainder of the loan dynamics do not change at all.  

Rental rates fluctuate with supply and demand like everything else.

That said, I question how much of that is coincidental, because homeownership rose for years and has only declined on a macro level for the last four years.Apartment values fluctuate with NOI, which can vary with occupancy, rents, and expenses.

Other benefits of getting a rental property below market allow for more negative market fluctuation so their is less risk.

This is a local market fluctuation that will be slightly different from one market to another.