Welcome, @Erconwald! There are dozens of threads on this forum to help you get up to speed and I’ll bet at any moment @Jenny will jump in to give you links to some of them.
Every sitter is different, but I prefer to NOT stay in the home the night before. It is so awkward, with the homeowners rushing around getting ready for the trip and me tiptoeing around with people I’ve just met. If it is essential, like with a cat who has an unusual medication routine, I will stay for ONE night with the homeowners there, but never two. My favorite homeowners are the ones who’ve written such a thorough Welcome Guide that I can show up without them there and everything is fine.