of dumb, irresponsible, short-sighted life choices (unforseen life tragedies are a different story) then you're setting yourself up for a crowded home in your "golden years". There's nothing wrong with telling them this, and also "Don't have kids until you are ready to take care of them ALL THE TIME, because I won't be raising your kids or free day care". It's just all about expectations.

I just can't believe how many empty nesters/grandparents in our ward have adult kids living with them and/or are spending 8+ hrs a day with grandkids. That's not my plan.