How involved should parents be in adult children lives?

Can parents and their adult children live in the same household?

Can the family live together as a big family for life?

For example I know this man and women married purchased a house and asked in laws (wife's parents) to move in for life they are doing a good job living together.

I believe parents should teach children as a teenager how to be a successful adult and show them real world skills about bills, about cars, about lawn mower, cooking, relationship advice life advice and financially help them if possible or help apply scholarship or fist job help them.

But most parents want an empty nest children gone doesn't matter if they own a castle.

Like some parents at 18 tell children to leave the house they don't have car, a house nothing its frightening and I believe is a bad job as a parent.

I feel like parents and children can coexist and live happy in the same household if there is positive relationship but I notice even if they have a wonderful child for example a daughter that's going to college, working buys her own stuff, groceries and helps clean the house she's quiet reserved but the mother wants her to leave. The daughter doesn't want to live with bad roommates or live alone she really wants to stay home what should she do?

I know they have Senior retirement centers that parents can live but some children care for their elderly parents or disabled parents why can't some parents have compassion or want to live together if the adult child is clean doesn't cause problems.

Why are some parents aggressive I have seen father's glare with hate at son's daughter's

I've seen moms treat kids coldly.

They say success is graduating highschool, moving out of parents house, graduating college, well paid well respected career job. Having a beautiful place to live Getting married.

But what about the bumps in the road can't afford college, don't have skills fancy job, can't afford a beautiful house, relationship failed married failed, had a child or children, had complications during surgery can't work, contraction life long disease from cheating husband. What about this what if you didn't get it right the way everyone expected

Ohana means family no one gets left behind or forgotten