If you are a professional photographer in the sense that you derive your sole income from your photography, then you might look at royalty free stock photography as a low maintenance form of income because you already have the volume ready to go and might have already earned income from it! As a professional photographer, you might submit your out-takes which have already been paid for in service fees on past assignments. Everybody else must build it up over the years! You will not make a living out of stock photography without the volume! So for everybody else, treat it as a hobby that just might provide real income in the next decade, or as a pension in later years! Make your priority fun as a passion you enjoy, but don't think about giving up your day job too soon! Remember you don't have to be a professional photographer to produce professional quality images!