at what age does it become strange for somebody to live with there parents?

Western governments are actively encouraging it.
One, because it relieves them of the responsibility of having to provide social housing. And
Two, because it relieves the government of needing to create sufficient care places in homes or respite care or hospital places !

And as economies continue to plummet given low wages and spiraling prices worldwide i'd expect this trend to continue.

I’d say 37 because by then you should have a well paying job

I'm not sure..I've seen a whole range of people who live with their parents for so many reasons. My best friend moved back in with his parents to care for them. Others moved back in after divorces..each case its own set of circumstances.

I don't think it's strange as long as you're contributing somehow. It's when you're an adult NEET (by choice) mooching off of them that I look down upon it.

Every family dynamic is different so it's hard to say. I came and went a few times from my parents until I was around 23 when I left for good.

There is no demarcation as such. With the current economy, more and more people choose to live with their parents for much longer.

not strange at your age. People are either staying at home or returning since everything is unaffordable to the average person

in the US, maybe 25
Some countries, moving out before you're married is looked down upon

I'd say never just to be safe, because I've no idea where I'm headed

30

80