Use lucrative to refer to a business or investment that makes money. The drug trade has proved very lucrative, if dangerous, for people willing to risk their lives to take part in it.
This adjective is from Latin lucrātīvus, from lucrātus, from lucrārī "to profit," from lucrum "profit." In Latin, lucrum also meant "greed," a negative sense preserved in the English phrase filthy lucre "shameful profit or gain." But there is no shame in the sense of lucrative––if you're lawn mowing job proves lucrative over the summer, you might be able to buy yourself an old car.