The lease controls when the landlord may end the tenancy and take steps to evict the tenant. If there is no written lease, the Colorado statutes control. The most commons reasons for eviction are: Non-payment of rent, violation of the lease provisions and "No Cause" if there is no agreement as to the term of occupancy. If there is no such agreement, the landlord does not need a reason to terminate the tenancy and can evict the tenant after giving the proper notice.
This ability to evict for "no cause" is limited. It does not apply to eviction from publicly subsidized housing. Also, eviction because of the race, creed, religion, sex, handicap, color, national origin, ancestry, marital status or familial status of the tenant is unlawful. Endangerment of person or property on the premises or committing a violent or drug-related felony on or near the premises.