Establishing that a landlord that offers a residential dwelling unit for rent is deemed to warrant the dwelling fit for human habitation; authorizing multiple tenants to join as plaintiffs in a civil action against a landlord and authorizing a court to issue an order for separate trials or other orders necessary to prevent delay or avoid prejudice; providing that a court may order certain relief in civil actions relating to the breach of warranty of habitability, including actual damages, abatement of rent, and lease termination; etc.