What are the risks of REI?

[Ryan Morgan]

I've been researching REI for awhile and am convinced it's a good investment. My wife isn't sold, and she has fair and valid concerns about the risk. We are financially stable with no debt besides mortgage, on pace for retirement, have kids with 529s, and have savings for down payment. I plan to use a property manager. So, what are the risks of REI? I'm factoring in vacancy rate in my calculations, along with 10% capex. She's concerned about housing market downturn, major house issues, and its risk compared to something like mutual funds. Thoughts?