I sent you a message, I've seen this before plenty of times and am able to help you with exploring your options.

And the second was that it was in a flood zone with the listing agent and seller saying it had never flooded but we were able to get confirmation that it had taken on water at least 3 times in the past year and the insurance agent for the property stated that with the flood insurance the premium would be close to $11,000 annually which meant the list price had to drop from $339,000 to less than $239,000 to make anything work.

(make sure you are budgeting for maintenance and management if you plan to use it) Rent will increase over time and your property will continue to appreciate in value. 

@Bradley Buxton makes a very good point to make sure to do your due diligence as you won't be an owner occupant like your in-laws.Last bit of advice: Because this is a friendly deal, you want to take your time to make sure you structure it in a way that maximizes tax and cashflow benefits for both parties. 

I don't have any real world experience at this time so I won't pretend to know, but I will be following and learning along with you. 

I would not renew their lease then find someone who can pay their rent on time and will obey your rules.  

I finally decided that it is time to come see what it is all about! 

With one duplex you should be focused on selling 99.9% of the time and .1% on the duplex.

We’ve got one big player that probably has at least 600 units with their own rental office and full time maintenance crew.

Make sure to keep your eye on the prize and do not spend too much time chasing after the next hot thing.