There are two kinds of rental agreements: Written leases and oral rental agreements.
A written lease will normally include the:
Amount of the rent
Duties to repair
Responsibility for damage
Whether a security deposit is required
Other conditions the landlord or tenant may wish to include
Oral Rental Agreement
An oral (unwritten) rental agreement is the relationship between a landlord and tenant(s) who do not have a written lease. Just because the agreement is not on paper, doesn't make the lease any less binding.
No Lease Rental Period
If there is no lease, the rental period is determined by the time period for which the rent is paid. If rent is paid every month, the tenancy is on a month-to-month basis. This means the tenant or the landlord must give the other one month's notice before leaving or ending a rental agreement. While the landlord is allowed to raise the rent or change other conditions of the agreement upon 30 days notice, the tenant may terminate the lease on the first day of the next month by giving notice to the landlord within 15 days of receipt of the landlord's notice of modification.