The arrangements you make for giving your guests access to your home depend entirely on your particular set-up. Obviously, if they are using the entire property in an exchange, they will need access, though you can certainly make certain areas off limits. Many exchangers even arrange to exchange cars and care for one another's animals. Those are details for you to work out with your guests.

If you are hosting 1-3 nights, you may give access only to their guest room within the hours you are available, use the help of a maid or manager, or whatever works for you and your guests.