B и T

And how much does it cost to rent a room in one of those 3-bedroom mansions?

Depends on the room and the location. In a small town, a regular small not-too-dilapidated one is 300-400 pounds. In a big city, it's already 600-900. But that amount usually includes all utilities and internet.

Added after 2 minutes

🤑🤑🤑

For that kind of money, I wouldn't live with random people.