I know the MLS has many teams owned by Anschutz.. But in other leagues around the world, is it a common practice for people to own multiple teams in the same league? In different leagues? Is it allowed elsewhere?
No, it's not okay in most other leagues. I know some Italian owners have teams in different divisions, but if they were ever to be promoted, they would have to sell. MLS is a completely different, single-entity system.