Can rooftop farming be a real business or only a hobby?

For most people, rooftop farming is best treated as a hobby and a source of fresh food for the home rather than a serious income business, and it is wise to go in with that expectation. The reasons are simple: a single rooftop has limited area, so total output is small, and the labour and input cost per kg is high compared to field farming, which makes competing on price impossible. Where it can earn a little is at the premium end, selling fresh, pesticide-free greens and herbs directly to neighbours, or microgreens to nearby cafes, but the volumes are tiny and it rarely becomes a livelihood on its own. Some run it as a small supplementary income or as a services business teaching others to set up rooftop gardens, which can be more viable than selling produce. Be honest with yourself about scale before investing in it as a business. If income is the goal, the numbers are challenging. If fresh home food, satisfaction and a small premium side income are enough, it is very rewarding.