They do work great for ac or supplemental heat. 

Investing is about finding creative ways to generate income, and they might not all be ideal but you can always supplement a lower salary by using things like wholesaling or rent to own options with very little if any money down.

I'm hoping to supplement my retirement and not really looking to take a "paycheck" prior to my retirement.

Who's to say that you can't buy a rental property, and use the cash flow to supplement your stock portfolio?

Of course remember to screen the actual leases and maybe even bank statements to supplement when you do receive them!

A lot of utility companies offer supplemental policies for delivery and drain lines - you could ask them along with the 3rd party carrier mentioned in the comments above.

I would say the biggest plus for the service is convenience and the time that it saves if you aren't familiar with different types of credit cards and negotiating with the banks.Great for supplementing your repair budget for projects.

I plan to use RE just as supplemental to my income, so I am trying to get my W-2 job settled and a little less volatile. 

Our goal is to have enough rental properties to supplement both of our incomes combined.

I am interested in RE investing as a means to supplement my retirement income and build a financial legacy for my family.