Real estate. I am semi retired. I built up little by little buying and selling residential real estate on the side.
There is definitely a migration from baby boomers retiring from north eastern states to the south that you can take advantage of (the retirees usually buy but they create jobs in the area for workers that most likely rent). Make sure that the rent in a particular area gives you a descent return. Just don't buy in Las Vegas, California, or Arizona like so many investors that didn't think. I have not been affected by the real estate bust.