why can't they build their own The Mets and Yankees can afford to privately build their own stadium. Why can't the Jets or Giants since the NFL makes more money.

not share a stadium

It's a sound economic solution that benefits both teams. The Jets tried to build a stadium in Manhattan, but that was soundly defeated by NY voters.

Also, the Lakers and Clippers share an arena in LA, and you don't seem to be complaining about that. And - guess what - if the NFL returns to LA with two teams, they'll have a similar arrangement.

because they both are too cheap to build one they would rather wait for the other team to move out

the jets ARE building a new stadium...it isnt finished yet