Complex sentence: Pérez built his fortune by building and operating low-income multi family apartments across Miami, then branched off into rental apartments before becoming one of the most prolific high-rise condo builders in the Southern United States.
Split into simpler sentences: Pérez built his fortune by building and operating low-income multifamily apartments across Miami. He then branched off into rental apartments before becoming one of the most prolific high-rise condo builders in the Southern United States.