Final answer:
An owner can make additional money from a 3-story building on property zoned for a 20-story building by renting out space, developing the property, or utilizing the rooftop.
Step-by-step explanation:
An owner of a 3-story building that is zoned for a 20-story building, and who does not want to sell the building, can explore different options to make additional money from it.
1. Rent out space: The owner can lease out the vacant floors to businesses or individuals who are in need of office or retail space.
2. Develop the property: If the local development codes allow, the owner can consider adding more floors to the existing building. This will increase the number of rentable spaces and potentially generate more income.
3. Utilize the rooftop: The owner can explore the possibility of adding rooftop amenities such as a rooftop bar or event space, which can attract more customers and generate additional revenue.