Ladyelaine, nothing in life is sure. I know a woman who was homeless as a teen, because her parents had died on the same airplane, and she couldn't inherit for years. The trustees wouldn't even help her arrange a loan. However, with roommates, clear agreements are usually followed. There are house meetings to straighten out any problems. Often, roommates are found within a circle of friends, but failing that, you can ask for references to weed out the psychopaths.
I chose life in shared houses for years to learn how NT families operate, and may have stacked the odds in my favour by selecting vegetarian homes. That seems to filter out the most disturbed, inconsiderate people.
The guests I met came with introductions and advice, which was far better than making cold calls to meet new people. Usually, I'd continue with what I was doing, but I was free to explore a new friendship.
There is a wide range of formality. Sometimes, people almost subdivide their apartment; others live like family, except through choice, not heredity.
The house parties are a great feature. You get the status of a host even with people who would otherwise wonder what you were doing there. I learned to enjoy dancing, and my musical horizons expanded greatly.