Multi-family housing real estate refers to residential properties that contain multiple separate housing units within one building or several buildings within a complex. These properties range from small duplexes and triplexes to large apartment complexes with hundreds of units. Investing in multi-family housing can be lucrative due to the potential for generating multiple streams of rental income, economies of scale in property management, and the ability to spread the risk of vacancy across several units. This type of real estate is popular among investors seeking steady cash flow and long-term appreciation, as well as providing essential housing options in urban and suburban areas.