Depending on local zoning and "offset" rules, McMansions can be built on very small plots.
Rows of McMansion-style houses have been built with very little offset by abusing rules intended for townhouses. In the cases I've seen, a single shared wall -- often just a token wall made of brick connecting two structures on the outside -- allows the McMansions to qualify as a multiple-family dwellings and obtain higher density, dramatically increasing profit.
A "unit" isn't necessarily residential. There are mixed-use "units" on the market that might be used as homes or as offices/shops.
A "dwelling" mostly comes up in the contexts of censuses and elections. One census form needs to be filed per "dwelling", and should include information about everyone who has dwelled there for the majority of the last year. This includes, for example, people just crashing on the couch, even if they're just on vacation and "live" somewhere else. For another example, this includes homeless shelters: the people staying in them can say the shelter is their "dwelling", though they're unlikely to feel like it's their home. (Also, a "dwelling" is not necessarily residentially zoned. You might be dwelling in a storage unit. It's not necessarily legal, but the government still needs a word to describe "places people live" that includes such cases.)
There's also "residence", which is just "dwelling" in fancier clothes, though usually implies residential zoning.
I'm not sure where you got that connotative sense for "dwelling". It shouldn't carry negative value - it's a very neutral term for a place someone lives.
"To dwell on" something isn't inherently negative either, it simply means to spend a fair amount of time thinking or focusing on a single thing. Whether that's good or bad depends on the context, and is not implied by the word itself.
... yes, I'm agreeing with you. And cringing as I remember a visit to a friend who'd taken up wine cellaring some years back, describing various vintages as "product". You'll hear that in media, app design, clothing, food, restuarants. Pretty much everything. MBA-speak gone mad.
I don't know much but in US I see home is very much used in type of house sense e.g. town homes, single family homes. Home does not give any warm fuzzy feelings here.
Rows of McMansion-style houses have been built with very little offset by abusing rules intended for townhouses. In the cases I've seen, a single shared wall -- often just a token wall made of brick connecting two structures on the outside -- allows the McMansions to qualify as a multiple-family dwellings and obtain higher density, dramatically increasing profit.