You cannot only be happy without lots of possessions, lots of possessions even make you unhappy. They hold you down. You don't even need to ask the old greeks for that, there are lots of contemporaries who can tell you that!
Of course, its easier to be happy with enough and nice food and a warm roof over your head.
But does working long hours in a job you hate just to get the second car and a bigger house to store more unused stuff make you happier?
You are right, happiness is far simpler than looking externally, happiness is as simple as deciding to be happy.
Dont forget we need to pay tax...1st thing to pay before getting our hands on our salary.