They don't generally have ill intentions but aren't aware sometimes of the ramifications seemingly minor actions have on the property.The answer for me is lots of on-boarding and coaching, some tolerable inspecting, open communication and trying to align their interests with mine.

This will depend on your tolerance for dealing with guests remotely. 

Not really enough (IMO) to turn on a heater but I guess everyone has their own measure of tolerance.

Unlike most landlords I do not tolerate late payments.

But you have to inform the tenant that things have become intolerable, and that if the tenant cannot tolerate the rental unit and you can't solve the issues, then moving elsewhere is necessary.Hey, nobody is perfect and tenants certainly won't be perfect - but you need to train this one differently it seems.

Most people seem to have a higher tolerance for odors and damage than I do.

While some of these are legitimate concerns when starting a business, they should never stop you dead in your tracks.The beauty of real estate investing is that the majority of these concerns can be overcome by simply choosing a niche that fits within your level of risk tolerance.

I'm trying to get a feel for others tolerances when it comes to the their total out of pocket expenses vs the cash flow (piti + vacancies + maintenance).Mine, maybe 20k out of pocket with a cash flow of at least $300 a month cash flow (after piti + vacancies + maintenance).  25k out of pocket for a $400 a month cash flow & 15k out of pocket for $250 a month cash flow.... 

IMO that would not solve the problem this tenant has, which I believe is they spend every "spare cent" and then discover bank fees or some other "emergencies" have eaten some of that "spare" money.As already mentioned above, rather than you training the tenant that you will not tolerate late rent payment without the late fees being paid, the tenant has instead trained you the landlord to allow the tenant to get away with this behavior with paying late.

You have to take it case by case, and you need to consider your own tolerance.