Finishes can vary in the thickness of the plating... the thicker the better. 

However it is oil based and a little thicker than normal paint.

But what happens is every once in a while you get a tenant that trashes all the carpet and now you have to deal with replacing it all.Its so much easier having the thicker vinyl plank so that you no longer have to deal with those kinds of turnover costs and effort.

No problems there just a bit thicker floor than usual.

I am guessing from the amount of stain on the base board and the fact you said the "floor guys" said it was thicker than normal it is excess stain. 

I would suggest you get some thicker skin as they say as this business will get you doors slammed in your face, people yelling at you for calling them on the phone, hate mail back for sending them mailers, and much more.

The only baby threshold I have seen is for MUCH thicker flooring than my 1/8"+ vinyl planks. 4) How small of a gap should I go with at this (slider) end of a 27' run?

These were intended to be wall tiles and are thicker than regular floor tiles.

Heck, a simple (thicker) blanket would solve the issue.  

I only selected your post as the title you used is a good one, it means more new folks may search the "how to start" aspect and find my rant, so, again, not really about you but thanks to you.And, to be in real estate, or to be in the used car business or to break rodeo stock or be in similar rough riding business environments, new folks need to have thicker skin, understand my personality at times is just that of an old kick butt Army guy, I'm not here to teach Sunday School.