We've only had to turn one of them into a rental (the first one), and in retrospect, we pulled the trigger on that WAY too soon...had we left it on the market for a few more weeks, we would have gotten it under contract (most likely).Having the possibility of a cash flowing rental as your backup plan is a great idea...will definitely help you sleep better at night.That said, if I ever have a flip gone bad, I'd likely sell at a loss before turning it into a rental.

In retrospect, I should have chosen someone like that, over an out of state tenant who had never seen the property or had anyone come and see it for them either.

In retrospect, we should have considered delaying the closing to contest the appraisal.

The listed price was so good (but really in retrospect, I should have negotiated), I just paid it.

In retrospect, it would have been easier to refiance using private/hard money even though I would pay a little more for it. 

I have had Medicaid question the sale of a house retrospectively, questioning the sale price because we bought below FMV, however, a letter explaining the price based on the “as is” condition of the house and the expenses required for renovate to get the house to FMV was sufficient.

In retrospect I'd have kept the 10 Plex off and sell any Multi-family via my network.

I have house hacked for a year and in retrospect, I paid too much for the property. 

Impressive at the time, but a loveboat-esque in retrospect.

@Matt Motil gave an excellent analogy about the crabs.In retrospect, the fact of the matter is that it's good for you to be able to share those experiences with this community which embraces your REI mindset.