If we were a type 2 or 3 civilization, could anyone colonize a planet?

Well, this is for a story that I am writing but basically in a world with an extremely large universe there would be billions of planets. The question is whether it would be realistic for there to be private planets, only that instead of buying them someone with money, a millionaire would simply put robots and build a private colony to exploit the resources of said planet and sell them, even set up factories to exploit that planet.

I also want to know what consequences it would have to basically take possession of a planet, what the consequences and risks would be because I would like to put difficulties in plotting and possessing planets.