Al Gordon explores the history and regulatory background of duplexes, triplexes, and fourplexes, noting that they were once categorized as single-family homes, despite having multiple units. These properties arose from a demand for income-generating assets, built by individuals seeking to create sustainable revenue streams. Gordon highlights the potential of investing in plexes as a means of achieving passive income and financial freedom. He emphasizes the importance of leveraging educational resources from Lifestyles Unlimited to gain knowledge about the best strategies for acquiring and managing these types of investment properties.