B.C.
I like garage sales in rich neighborhoods, especially on the last weekend of the month when people are just before the next paycheck. Or the first of the month if the first is a Saturday when a lot of people are at the bank, trying to cash their check.
My daughter uses freecycle.com and there are several like that.
Drive the rich neighborhoods on the evening before "trash day" when the rich put their trash out by the street. Its not uncommon to find nearly new trikes or bicycles in the trash.
Then there is always Deseret industries, Goodwill, and the Salvation Army and thrift shops. I've seen trikes for $5 and bikes for $10.