The apartment at the upstairs would be available for rent, after Erin moves out.
Ask Lefty about the room. You should first fix the brewery.
This is the low-spoiler guide for "Getting a room" puzzle in Leisure Suit Larry - Wet Dreams Don't Dry. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.