Exactly. You're paying a realtor to promote your house, including on their site, to sell it.
Zero difference from hiring a TV channel to promote your product, on their channel, to sell it.
Which is why trying to define advertising in a way that bans it is not simple at all.
GP says "Publishing factual information in a place people expect to find it is not advertising."
OK. Now the realtor adds a blog. They start publishing news about the real estate business. With listings mixed in. Congrats, you've got a newspaper with ads for homes. Are you ready to say the realtor can't publish news? Isn't that censorship?
Also, home listings aren't "factual". They're promotional. They focus on pros and omit cons. They have photos that hide the ugly parts. They're ads for homes, period.
Surely there is a difference between me (private person ) selling my 1 car/house or company Y advertising their latest car model (they want to sell 1000ds).
Yes, there's a difference in the number of items you're selling.
There isn't a difference in terms of the fact that it's advertising a sale. Nor is it relevant if you're doing so personally, as a sole proprietor, as a partnership, as an S corp or as a C corp. Advertising something for sale is advertising something for sale. Ads are ads.
Also, on the realtor's site they're listing hundreds of homes. Not any different from your local car dealership advertising their hundreds of vehicles. They're both corporations listing ads.
According to the definition given, if the intent is to "promote a product", and money changed hands it is.
It also meets websters definition of advertising:
> the action of calling something to the attention of the public especially by paid announcements