I have a 85+yo tenant on the top floor ; been there since he retired,   and another 70+yo retiree on the 2nd floor.     

My goal however is to not solely buy and sell houses but to invest in properties for passive income into retirement.

Buy in more recession proof corridors of the United States less dependent on one or two major industries, or with a large government base, or with a retirement or tourist community.Disadvantages of Buying Out-of-State-Multiple tax filings, deadlines and other local taxes due.

Next is to take stock of your goals (for example, accumulate wealth for retirement, quit your job, etc) and be able to articulate them clearly.

Need a back up plan for retirement.

It took me years to find a guy who was an analytical thinker, even though he did not own rentals he understood better than anyone else.Spending the time to find an agent who has walked the path you want to be on is probably the best investment of your time early on in your career.Many years later I got out of the rat race and "retired" from corporate.

When I went from owning a home to renting at retirement, I had neither an income nor a previous landlord.

I'll also add that I invest retirement money differently from non-retirement money.

If you have 500k -1 million dollars I would say 50% should be in a retirement fund, the next part is up to you. 

Here's a few reasons why:Travel nurses already go through background checks and drug tests so you know you're getting a reliable tenant.They get paid really well AND get a housing stipend so getting rent paid on time is never a problem.The demand for travel nurses is only increasing with baby boomers retiring, so you'll always have a stream of tenants.For a furnished home (or room) you generally can charge a higher premiumTravel nurses generally work 12 hour shifts and love to sleep as a result... no noise complaints from neighbors.Their contracts are typically 13 weeks.