I would take exactly the opposite view. I live in the SF Bay area. My home is worth about $600K. If I rented it, I could probably get about 2800/month. If I have 20% equity, thats $200K. After mortgage/tax/HOA it would leave me about $300/month positive. Thats not including maintenance or vacancy. So at best its a zero cash flow investment. If it is vacant , the cost is huge.
It only makes sense to do this if I am expecting great appreciation or if I am renting it for a short term and intend to use it again as a primary residence.
Now instead of one home for 600K, I could get 12 homes at $50K each. Each would rent for at least $800 for a total rent of $4800/month. Yes I may have some vacancy but the fact that I would have 12 would make the impact of any single vacancy not too bad (8%). While I may have more vacancy than the expensive home, the number of homes makes the risk spread out.
I would never buy a luxury home to rent out. I would buy it to live in. Think of it this way, if you were running a taxi service would you buy BMWs for your fleet or Toyotas?