Why is it so important for a tenant to sign the lease first? The lease is a formal contract between a tenant and a real estate owner or a representative of the owner, such as a house manager who describes the living conditions in a rented property in exchange for the rent. Due to the short duration of a rental agreement, they allow much more flexibility when it comes to increasing rents. From a technical point of view, the rent can be revised each month with a lease in order to remain in line with the current market rent, as long as the rent increases comply with local law and the termination clauses that govern the monthly rent. No, but a landlord usually requires that anyone who lives in a rental unit be mentioned on the lease, either as a tenant or as a resident. Landlords have the right to know how many people live in the rental unit and who lives there.