@Nancy1282 The best thing you can do is be as clear as possible with shared spaces. Lately I have gotten a lot of longer term travel nurses and med students because I am close to a hospital. I clear out 2 shelves in the fridge and pantry for them and let them know during the home tour/welcome that these are specifically for them. I also reiterate any rules I find very important, such as quiet hours or off limit areas. This helps establish a clear understanding from the start as some guest fail to read the rules in the listings.
As for him playing the guitar, as everyone else said unless it is at a late hour, or obscenely loud, it really is not a violation of anything, unless you specifically have rules against this. If you are a person who enjoys a more quiet atmosphere at all times, hosting is going to be a tuff ride.