How long did Paul live in his own rented house in Rome, welcoming all who came to him?

Answer: Two full years

Paul stayed two full years in his own rented house (KJV: hired house), boldly proclaiming the kingdom of God.

“Paul stayed there two full years in his own rented house, welcoming all who came to visit him. Boldly and freely he proclaimed the kingdom of God and taught about the Lord Jesus Christ.”— Acts 28:30-31 (BSB)