Hcfyk

Not long ago, I had a conversation with a gentleman working at my building. I asked him if he lived in the building and he said "No I live in a home."

I thought that was a strange wording, but I understood. I may have heard this phrasing once or twice before (in the Midwest United States). Home is a fancy synonym for house. People in America often talk about "finding a home", and usually mean a single-family house. But my understanding of the word home has always been just a place where you live. That is the first result on Google, which doesn't mention "house". Merriam-Webster does include house as a synonym in definition 1b.

Just today I was talking to someone online, not local, about apartment problems, and I used the word home for apartment, and they said something like "No it's different for people in homes."

So it wasn't my imagination or just a weird quirk of the midwest. This is considered acceptable usage in English, although maybe not common? When and where did this specific sense of the word "home" originate? Is it a recent construct or something I've just not noticed most of my life?

This answer addresses mostly the use of the word home as a synonym for house, and just in the United States. I do not yet have a real answer, only a plausible possibility, for when the use of home started or became widespread.

My source is a chapter in the book Class; A Guide Through the American Status System by Paul Fussell. The chapter is "Speak, That I May See Thee", which is the closest US analog I know of to the British U and non-U English popularized by Nancy Mitford. Both works -- Mitford's and Fussell's (published in 1983) -- may be somewhat out of date now that money has come to be of such overwhelming importance, but I can testify, as a US native of too many decades (BosWash Corridor), that Fussell rings true on his discussion of home vs house. Fussel is a curmudgeonly sort, and something of a snob, but he got it right on home.

All classes except sometimes the upper-middle are implicated in the
scandal of saying home when they mean house.
"[Example]....they live in a lovely five-hundred-thousand-dollar
home." We can trace, I think, the stages by which house
disappeared.... First, home was offered by the real-estate
business as a way of warming the product [as not] a passel of bricks,
wallboard and Formica but snuggly warmth, comfort, and
love......[several modest reasons why home caught on, followed by the
hilarious]...(3) [to] the middle-class ...... house carried bad
associations. One spoke of a rest home, but of a bawdy, whore-,
fancy, or sporting house.

I don't know about #3, but it was too good not to include. But note that the bordello owner, Polly Adler, wrote her very popular book A House is Not a Home in 1953, which is about the time I postulate that home replaced house -- see paragraph below.

This paragraph suggests that home became popular in the great post-WWII house-building boom of the late forties and the fifties, when restrictions on using building materials for non-war purposes were eliminated, the economy boomed, and suburbs spread over the land.

As the comments have mentioned, the word home has not become fully synonymous with "house" in general. The meanings are similar, and some people may sometimes use "home" to mean "house" in the sense of "a separate building that serves as a residence for one household", but it isn't a usage that has become firmly established in current speech across the English-speaking world. (I don't know whether there are any specific regions where this usage has come to be usual.)

I doubt that this usage is particularly recent. More specifically, I'm sure that it is possible to find examples of people using "home" in the sense of "house" before anyone currently alive was born, so I'd expect it is "something I've just not noticed most of my life": an example of a recency illusion.

The Oxford English Dictionary entry for the the word home has an example of "homes" being used to mean "houses" from 1882:

Harper's Mag. Dec. 58/1 A lovely drive..is bordered with homes, many of which make pretensions to much more than comfort.

When I googled this quotation, I found a discussion of this topic that says that "seven years later" (i.e. in 1889), there was a real estate advertisement in the Kansas City Times and Star reading "for rent, a fine home at 1223 Broadway" (p. 71, "What You Mean by Home", in The Work of Poetry, by John Hollander).

As others have pointed out, in many (most?) places and contexts, "I live in a home" doesn't mean the same thing as "I live in a house." But in other contexts, "home" is synonymous with "house." For example, I think in common usage, especially in the real estate industry, "homeowner" only includes owners of single-family houses:

This is one of the primary advantages of living in a condo. While homeowners are busy mowing their lawns, painting the house, trimming hedges, cleaning gutters, pruning trees, raking leaves, and shoveling snow, condo owners are busy hanging out at the pool, taking weekend trips, or simply relaxing at home.

https://www.moneyunder30.com/buying-condo-vs-house

But for purposes of the US Census, homeownership appears to include all owner-occupied housing, whether it an apartment in a larger structure or a detached house:

Homeownership Rates. The proportion of households that are owners is termed the
homeownership rate. It is computed by dividing the number of households that are owners by the total number of occupied households (table 5 and 6).

https://www.census.gov/housing/hvs/definitions.pdf

In this definition, "home" includes any kind of household. It also shows another facet of this issue, which is that "housing" refers to any kind of dwelling where people live, and "household" refers to any group of people living in a single housing unit. Neither of those terms is limited to what we'd normally consider a "house."

Basically, the usage surrounding these terms is very complicated, and very dependent on context. In some situations "home" can be used to distinguish "house" from "apartment", but not in others, and in still other situations it can refer to something completely different than either. Looking at the examples you provide above without context, I would interpret, "No, I live in a home" as "No, I live in an assisted-living facility."