Installment plans were credit systems where payment for merchandise/items is made in installments over a pre-approved period of time. In the 1920s, the items people could purchase with an installment plan included: automobiles, automobile parts, household appliances, radios, phonographs, pianos, and furniture. People were so in love with this new idea in business because like any new concept, everyone thinks that it has no problems or downsides to it. People essentially thought that they were getting things for less/free because they were not being forced to pay apon purchasing. This created a false sense of security and obviously people fell behind on their payments or even lost their jobs and were left with no way to pay off all of the things that they had bought. When people lost their jobs and could no longer make payment that were bought from the store or company that set up the installment plan, banks started to lose lots of money from unpaid installment plans. All of these unpayed loans contributed to the Great depression in 1929.
Above is an ad for a typewriter on an installment plan. Normally a pretty expensive item, people were attracted to the thought of playing later rather than sooner.