Can I sell azolla as a product or is it only for my own feed?

Be realistic: azolla's main value is as a low-cost feed supplement on your own farm, where it saves money by partly replacing bought concentrate. There is a small market for azolla starter culture (selling fresh azolla to farmers who want to begin a bed) and sometimes dried azolla, but it is a niche, not a big organised market, because azolla is cheap and easy for anyone to grow themselves. So do not plan a business on selling azolla like a crop. The dependable benefit is reduced feed cost for your cattle, goats, poultry or fish. If neighbours want to start, selling starter culture is a modest extra. Treat any income claims with caution and confirm local demand before scaling beyond your own feed need.