Very common in London and as others said other big cities, some seaside communities etc.
I think I'm one of two 'poorer' families on our street. Houses aren't dissimilar as it's a mix of mostly terrace and a few detached. The detached (3) are by far the most uppity, regularly complaining about all manner of things. One is the ring leader and she is very loud in her opinions. Ironically they moved onto the street when it was a dive, so it always makes me chuckle slightly that she thinks they are so well to do.
The houses in our street have gone up x 4 in the last decade and are now no longer a dive. It makes for quite the division in terms of mortgages/disposable income, but it is the people who've been there the longest who seem to have the most disposable income - for example employ dog walkers, two week holidays annually, members of private clubs. Their job/incomes may be far less than the young couples who just bought and have been saddled with huge mortgages and will be house poor for the next decade.
Richest - Three families stand out. One had huge inheritance at age 40 and hasn't worked since. Misers. When drunk at the street party was telling everyone how he safely invested the 2 million 20 years ago and no one has seen a penny of it since because he's not letting his family throw it away. They have never taken a holiday, never eat out, never get a take away, never decorate, and brag about making clothes last for decades. There was even a big fight when wife wanted to paint the lounge, repeatedly saying how they have three million quid in the bank and she can't even paint the lounge. It was a hot day so windows open and everyone heard. ha ha. They won't even pay for internet or a tv license!
Other couple it's their disposable income that gives it away, kids in elite sports, private club membership, dog walker at 25/quid day, expensive private play schemes and Mum a SAHM for 16 years. Though like someone's SIL if she had 90% of the world's wealth she'd complain about someone having 10%. That's her to a t. Pleasant enough but very entitled.
Final couple have 2 luxury vehicles and 2 rental properties but live in a terrace that is actually one of the smaller ones. Their rental properties are in the road behind us with flats and the two rentals are easily worth over a million combined.
The two poorist - single working Mum's, myself one of the two. Both work more than one job, both of us take lodgers through the same program late spring/early summer. The outside of my home you may not be able to tell, hers is a little less appealing to the eye. We definitely don't have the same lifestyle as many neighbours in terms of holidays.
But we all live on the same street in very similar houses except for the 3 detached and except for the one family with luxury vehicles, you'd honestly never be able to tell from the outside.