Hey everyone, Here is my solution for Checkpoint 8 and as always I am open to any feedback you might have. Thanks! :)

protocol Building {
    var type: String { get set }
    var rooms: Int { get set }
    var cost: Int { get set }
    var realEstateAgent: String { get set }

    func salesSummary() -> Int
}

extension Building {
    func salesSummary() -> Int {
        let commision = cost / 10
        print("\(realEstateAgent) earned $\(commision) commision for selling \(type) for $\(cost).")
        return commision
    }
}

struct House: Building {
    var type = String()
    var rooms = Int()
    var cost = Int()
    var realEstateAgent = String()
}

struct Office: Building {
    var type = String()
    var rooms = Int()
    var cost = Int()
    var realEstateAgent = String()
}

let house = House(type: "house", rooms: 5, cost: 1_000_000, realEstateAgent: "Betty")
house.salesSummary()

let office = Office(type: "office building", rooms: 100, cost: 10_000_000, realEstateAgent: "Bob")
office.salesSummary()