Congratulations to your son on receiving enough interest to warrant a home visit. That is a good sign.
Our experience was that the only thing that was expected of our son was to be ready to talk about his thoughts on his baseball future. Would he be willing to sign out of HS and if so what would it take for him to do so. By the way we never spoke of actual $$ in the early conversations just mentioned what rounds it might take to make it appealing enough to him. That gave the scout a general idea of what kind of money he was looking for. Many asked what kind of commitment he received from his college so they could better tell if he might be a tough sign. Much of the college and round questions were centered to my wife and I as well.
Some teams administered a Psych test and a couple did eye test as well (our son was a pitcher so the eye test may be more in play for position guys). Our son recovered from a shoulder injury the year before his draft so we had copies of his medical records available as well because most asked for them.
Other than that, we offered the scout a drink and that was about it.
Good luck...feel free PM me if you have any additional questions.