Joint and several liability, explained without the jargon
When a lease says tenants are jointly and severally liable, the landlord may seek the full amount due from one tenant, several tenants, or all tenants, subject to the lease and law. Your private agreement that each roommate pays one-third does not usually limit the landlord’s rights under the lease.
That is why roommate screening and a reserve fund matter. Pay the landlord on time if you can, document any shortfall, and resolve the internal debt separately. Do not assume a landlord must chase the roommate who caused the problem first.
Before signing, ask whether the lease has this clause and how a replacement tenant is handled. A local tenant organization or lawyer can explain the risk in your exact agreement.