Apartment Investing refers to the financial activity involving the purchase, ownership, management, rental or sale of apartment properties for profit. It encompasses aspects of real estate investment including the acquisition of apartments, subsequent property management, and eventual sale or rental. The category also incorporates the DIY aspect, where investors may undertake renovation or improvement projects themselves as part of their investment strategy. It aligns with hobbies as some individuals engage in apartment investing not solely for financial gain, but as a personal interest or pastime.