you can read(translations) of Davinci's note books where notes in the margins are to make more convex mirrors, which he sold for proffit to wealthy household, and to give money to his housekeeper and pay employees and buy all the things needed for his research, and all kinds of trials and tribulations involved in what was a wholely self funded operation. Yes, he had patrons, but many of them were fickle and didn't follow through,while taking up a lot of time, and then as now, the bills keep comming, and more than once he barely avoided destitution.