Welcome.
If you look at well covered subjects like the Golden Gate bridge (over 7,000 images on SS already) I think you'll quickly realize that for stock, you're better off focusing on things that are less plentiful in the collections but which may still be in demand.
Your locked water tap is a good example. It's the fourth image on the first page of a search for california drought (which has about 1,400 images). If you have access to things that illustrate the drought, measures to deal with it, etc. that's a much better use of your time (for stock) than tiger pictures.
Black and white generally doesn't sell well (any designer can make a b&w from a color image).
Good luck!