500 year flood zone properties - are they worth it?

[Li Smith]

I've still got a fair bit to learn, and money to save, before I'm ready to start investing. But I'm also getting older and I know youth and energy won't be on my side much longer when it comes to fixing up rental properties, so I'm sweating it a bit. 

While trying to research possible advantages I could look into that may tip deals in my favor, it occurred to me that in my area, there's a lot of flood zones, and a lot of people unwilling to touch them, period. I had a basement prone to flooding in my childhood and I clearly remember all the hard work it took my parents to keep it in shape, and while the idea of having to put that much recurring work into an investment property isn't appealing, I know what's involved and I'm debating taking it on if it means it could be a very good deal. I should add that my childhood basement was finished, whereas I'd only be looking at properties with unfinished basements here if they're in flood zones. So I have an idea of how much work it should take to preserve a finished vs unfinished basement. 

I want to know if anyone here has lived in/owned properties with 500 year flood zones - how often did they actually flood, more or less, how MUCH did they flood, and has anyone encountered any serious issues with concrete, unfinished basements flooding? How hard was it to protect the equipment - oil/gas tanks if any, exposed piping, boilers, etc? Did you ever have a serious flood, like over a foot of water? If equipment and piping was seriously damaged, how much money/pain did it cost to repair it? Do you suggest allowing tenants to use those basements if they agree to be responsible for keeping them dry within reason, like providing a dehumidifier or keeping one running that you provide? 

I really appreciate any feedback anyone has to offer, even if it's negative, as I don't have anyone I know locally I can bring these questions to. My friend and mentor in investing is someone who won't bother with flood properties, so he doesn't know anything about them.