You do not have to charge a security deposit, but it is highly advisable. For a furnished dwelling, a landlord can charge as much as one and a half month's rent. It is important to remember that if you are renting to roommates and charging each person a security deposit the total cannot go over the legal limits.
Some landlords try to charge nonrefundable pet or cleaning deposits or fees.
The legality of these is questionable primarily because of interpretations of the law regarding security deposits. Their usefulness is questionable as well. Tenants are often less careful about cleaning if they do not have the deposit return as an incentive. Also, if cleanup or repairs cost more than the fee, it could be argued that the fee is the limit of the tenants' liability. If you expect abnormal wear and tear because of certain tenants or pets, or you need more income to cover your standard pre-rental cleaning and improvements, you should probably simply charge more rent.