If a tenant does not pay the rent, in New York, as in many other states you are not allowed to lock her out. Generally, a landlord is not allowed to use "self help" to

evict a tenant. You may not lock out, throw out, cut off utilities (power & water), or take the law into your own hands in any way. You must use the judicial process: you must sue the tenant in court, giving her notice (a "summons") of the lawsuit and a chance to defend herself. If you win and obtain a "judgment," and the tenant still won't get out, you may then have the sheriff or marshal physically throw the tenant out. Make sure that your apartment managers understand this. If one of them uses self help, you are likely to be sued by the tenant.

The Eviction Process in General:

Serve a proper notice on the tenant
Unless a tenant refuses to leave after a fixed-term lease expires, you must begin the eviction process by serving the tenant with a notice. A 30 day notice terminates a month-to-month tenancy. But a shorter notice (usually 3 or 5 days) terminates any tenancy (fixed-term lease or month-to-month tenancy) where the tenant has misbehaved in some significant way - usually by failing to pay the rent, but also when the tenant damages the property or violates the agreement (e.g., by having a pet in violation of a no-pets clause). Often the misbehavior notice must give the tenant a chance to remedy the problem instead of vacating. in real property cases.

File a proper lawsuit against the tenant
When evicting a tenant, if the notice period expires and the tenant has not done what the notice required, the landlord may file his lawsuit to evict (sometimes called an "unlawful detainer" suit or "dispossess" suit or something similar). You may handle the suit yourself, but this is usually a bad idea. Since the suit seeks to "forfeit" the tenant's estate and evict her from her home, and because eviction suits are given special privileges (such as priority on the court's calendar), the law usually requires landlords to "strictly comply" with all technical legal requirements. It is very easy for someone not a lawyer to make mistakes in eviction suits and this might cause dismissal of your lawsuit and result in teh tenant getting a judgment against you for her costs and perhaps even her attorneys fees. If you want to evict, see a lawyer who specializes in these cases.