A 5% physical vacancy might be correct but you will probably have the occasional non-payer that takes a month to evict. 

Sometimes wells have reduced flow in the winter due to water table fluctuations if its a shallow well, so you may only need to supplement with an occasional water delivery.

There is an occasional thread on BP where the vendor has a system crash of technical glitch and transfers are delayed.

I have a house that the mainline gets clogged occasionally (it has been scoped, there is nothing wrong with it) but it always seems to be at noon Friday and then by the time you get a call its 6pm, and you're stuck with after-hour rates all weekend, etc. 

I think in most cases foundation repair is temporary....occasionally can get fixed if you fix the issues that caused it, but can't always do that.Lifetime warranty is a sales buzzword.   

Once our rooms were filled and leases signed - aside from normal cleaning and the occasional house project - our investment became almost entirely passive.

If you’re doing this because you see a market niche, and you can withstand an occasional loss, then that’s fine.

I also occasionally buy from owner financiers as well. 

There aren't a ton of duplexes over there, but they do come up occasionally.

I usually use it to show them that they have to the power to leave a place they don't like, and yes, occasionally use it to show them that I have the power to make them move too.