What are some reasons that people become homeless?

i think the main reason of homelessness is economic problems.
i heard that in the united states case,
if a person who doesn't have enough money gets sick, the person might becomes to homeless
because they have bad insurance systems
In any country, if you come to a situation that you can't earn money and your son don't even help you
you can become to homeless
there is a magazine called 'big issue' for homeless people in Korea
it is where that they sell it in to a person in front of subway stations and make them save up the money for their independence