Of course you re welcome to search other schools as well. Contact the potential seller through email. Decide on an appropriate price and arrange to make the book exchange. Please be careful in making the physical exchange by meeting in heavily trafficked public locations or by bringing a friend along with you. Of course you can use postal mail or other courier services if you prefer not to meet in person.
Any book is fine but students are usually looking for course materials.
This is between the buyer and the seller. Payment can be in cash, check, or in trade. It s up to you.