I've been doing a lot of pet sitting for cats lately. I see that some people place their cat's food and water bowls near the litter box. Perhaps this is a done for convenience, but litter boxes should be placed elsewhere, not near your cat's food and water, and preferably in a place that's quiet and private with enough room to turn around. Litter can get thrown into food and water bowls if placed too close. And that's not healthy. This can also lead to many issues including cats not wanting to use their litter box and going some place else!
The rule of thumb for the number of litter boxes is one for each cat and one extra. For some folks who live in close quarters, this might be too many litter boxes, so be sure to keep them very clean! Choose a box that's large enough and one that's not too deep. Cats like one to two inches of litter. Some cats do not like a hood that covers the box and others don't like the liner. Experiment with kitty's box and observe how your cat behaves. She'll give you all the clues you need to keep her "bathroom" space the best it can be!