Can I Use A Turf Pad Indoors Exclusively?

Hi. I'm looking at getting a small breed puppy. I live in a desert environment and there is no grass around, only rocks and cement basically. Is it ok/humane/healthy to use those disposable live grass pads in trays indoors? I would still provide the dog with at least daily walks and we do have a dog park in my community that has grass but it's not convenient for frequent use. We also have a large coyote population so letting the dog out in my yard (which is mostly rocks anyway) isn't really an option. I know people who live in apartments in cities use them but I just want to make sure this is a reasonable solution. If so, is it ok to only keep it indoors or should I put it outside? And is it ok to use these indefinitely beyond the training stage? It does regularly get to 115 in the summer here so there's that. Thanks for your help.