During the 1920s, people would buy stock on margin, which meant that they

bought it on credit.
paid cash for it.
paid in installments.
bought it on speculation.

For the answer to the question above, in the 1920's people bought stock on margin which meant that they could hold the stock for as little as a 10% downpayment. They also bought the stocks by credit.They wait for the stock price to rise and then they sold it.