Brandon Turner does a great job going over different strategies in his book "Invest in Real Estate with No (or little) Money Down".

If yu claim one it doesn't void the option to claim the other one.Provided you meet the IRS requirements for both, as a tax strategy, you could complete exclude a portion of capital gains under Section 121 and then defer the remaining capital gains under Section 1031 (@Dave Foster is a great resource for 1031 exchange). ..

Columbus also has great macroeconomics - lots of job growth, population growth, and major employers developing here.

I'm a small business owner and my partner has a corporate job. 

It’s super important you prioritize the end product: something that gets the job done well as an STR.  

While the co-signers add some security, the family’s newness to the U.S. and uncertain job situation make them a higher risk overall. 

There is still money down required but helps ease costs

It might be helpful to narrow down your options by focusing and researching for markets with strong rental demand, growing job markets, and property prices that fit within your budget.

With their low income and it's unlikely they'll get a better paying job.

Florida's treatment of security deposits varies from many states in that it is required that a security deposit be kept in its own account in a Florida bank.