Licensing depends entirely on the municipality, and there's no single national requirement. Some cities have a rooming house or boarding house license with its own inspection, occupancy limit and annual fee. Some have a general rental registration that applies to any rented dwelling regardless of how many leases are inside it. Some have neither. A few states also require a license once you cross a threshold of unrelated occupants or start providing services like cleaning or meals. The only reliable way to know is to ask the city's licensing or code office about that specific address and get the answer in writing, and if the answer is ambiguous, a local attorney is the right call rather than a forum.
Insurance does change, and this is the part people get wrong most often. A standard landlord policy, often a dwelling fire or DP-3 form, is generally underwritten with an assumption about how the building is occupied. Multiple unrelated adults on separate leases is a different occupancy from one household, and carriers treat it differently. Some will write it, some will decline, some will move you onto a commercial or habitational form. The risk isn't the premium. It's a denied claim later because the application described something other than what you're running.
One definition worth being precise about since you're building a service around this: co-living usually means the same thing as room rental legally, individual bedrooms leased separately with shared common space. The marketing difference is furnishing, cleaning and community management. Regulators look at the leases and the occupancy, not the branding.
