LIFE ON TITAN
You do not need to buy all of the hangars in a crater before special hangars, like pirate's hangars, become available for sale. You only need to consistently kill off all priates occupying the hangar and checking the local real estate dealer for the hangar's listing. It can take quite a few kills before a particular hangar is listed.
Below are two images that show pirate hangars for sale at different real estate dealers. Note the selection arrows beneath the image of the hangar. These show that there are other hangars available in the crater. You do not have to buy all of the hangars in a crater before pirate hangars become available.