Cost of flying

I am new to this newsgroup, and kind of new to flying. (Took lessons
exactly 30 years ago = 53 hours). I am on my second lesson.

Question. Trying to figure the cost of airplane ownership. Is insurance
mandatory (Oregon resident) or is it strictly to insure MY airplane, if I
wish. If mandatory (public liability?) what would some typical costs be
for, say, a C172, at my low hours. By the time I am licensed I will
probalby have a total of 100 hours, although only the last 50 would be
recent.

All replies appreciated.

Ivan Vegvary
Sandy, Oregon