What circumstances would make the owner a potentially motivated seller?

That being said, in some circumstances I would prefer to have more than one person reaching out to me to make sure I was serviced. 

It is my understanding that none of those circumstances exist in my case.

I have been on the opposite side where the plan was to hold the property and had a partner who life circumstances change i.e. their daughter is getting married and they want cash, they lose a job, or their credit gets ruined and then they cannot refinance.

Or what would have to be the circumstances of that to happen.

When doing high end flips, be sure you have a back up strategy in case the market turns on you due to circumstance beyond your control.

Yes, under the right circumstances you can charge an extra fee for this, and you can treat it as if the rent has not been paid with late fees and such.It is criminal to knowingly and purposely pass a bad check.

I have run into similar issues while renting, and made due with the circumstances.

Does this mean that under no circumstances I can require 60 day notice on a M2M ... even if the tenant agrees to it in writing? 

Except for certain limited circumstances I usually recommend against them, at least for long term buy and hold.