Both types of properties, however, can have ADU units (technically called "companion units") added to them. 

This is more of a hard plastic mesh and might not lay down as easily as the truck is driving forward.

That included pumping out, visual inspection, verification of leach field, re-fill with clean water & replacing the cover with some stupid green plastic thing the county now requires & which could be taken off by any 8-year-old.

Is a portable plastic swimming pool an "improvement" to a property?

Plastic rusts.

If the siding is exposed, wet it down before cutting and capture all debris on plastic and properly dispose of it).

How old is the building and what kind of waste water plumbing does it have (cast iron, plastic, etc)? 

Band-Aids – Made out of non-biodegradable plastic.

Noticeably nicer than black plastic numbers on the door like the rental units.

When the foam cures, tape a clear sheet of plastic over the filled hole and monitor the plastic for a week.