When their neighbor was evicted last spring, eight residents of a Downtown Brooklyn corner rowhouse took over his third-floor rental and turned it, with their landlord’s permission, into a collectively run, four-room bed-and-breakfast called 3B. Now, after a year of renovations, the insta-hoteliers are welcoming crashers. Nightly rates range from $40 for a twin bunk in the shared room to $160 for a private two-queen suite. Homemade frittatas, baked goods, and, naturally, granola are served in the morning (136 Lawrence St., nr. Willoughby St.; 347-762-2632).