I mentioned above that in my opinion right now, unless you are extremely talented, experienced and have the time to analyze deals and find markets that are attractive, its getting more challenging.  

Anywhere you have low lying areas close to water you're going to have an added carrying cost for flood insurance (unless 100% equity).  

The repair costs seem low for the Midwest

In NJ, margins are fairly low.

Recently we have been considering expanding our portfolio to mobile homes because of their low cost.

@Daniel Dietzfrom my perspective it does seem smarter to take advantage of these record low interest rates. 

If you install salt system and automatic cleaning your maintenance will be fairly low.

I believe a lot of our investors have success because the rent to value ratio makes sense, our PM is 8% and also our taxes are very low (I'm in Kansas City.)

When things went "pop" south of the 49th and we watched them slide off the tracks, there was an about face in Ottawa (a slow one, but it did finally happen) and regulators for residential real estate financing started to reverse course.It is still easier to borrow to buy real estate than it was in the 80s and the unprecedented run of low - almost no - interest rates has helped fuel the continued rise of several real estate markets in the country which should have gone "pop" themselves some years ago.

Owning a lot of SFHs for cash means low levels of risk, but also lower levels of return, since cash locked into a home is only performing at the rate of return for that home, rather than leveraged for maximum return.