(Fair disclosure, I've written about 200 estimates in the past 12 months.)Bizarrely enough, the bigger the job the less time it tends to take...

The "gap" should be at least 30%, and more if your market is slow for the type of house you're buying (winter is coming, and tends to slow the market too).

Other cultures tend to have stronger family ties and can make these situations work, I don't see this becoming the norm in the US at least not in the foreseeable future.

A property that hits a 20% return on paper but ends up needing repairs to keep a tenant inside can deminish returns quickly.Another aspect is that slumlords tend to look only at cash flow, the value of the properties is low and to keep the same or highest return, repairs are not made as they don't generally payoff immdeiately.

I tend to like the privately traded ones.

He tended to have 13 subjects so he would be more expert in each of those subjects every 13 weeks, or 4 times a year.I have 9 main tools in my toolbox and so I have the tool I need for the job almost every time, except for the rare exception when I have to dust off an old tool on the old tool rack and use it.

I find that single family homes that need work have less people looking at them as investors (compared to multi), and when they are cash only deals that tends to eliminate a lot of buyers. 

How much lower does it typically get, how long does it stay that way, and what tends to happen afterward?

An investor tends to be more savvy than the average consumer/home buyer.

I tend to think the more money I keep the faster I'll be in a position to do the next deal.