How long is a person who does not pay rent allowed to stay ina home once they are asked to leave?
If the person does not, nor ever has, paid rent (or any form of rent such as utilities or food), then under the law they will be considered to be a "licensee".  That is someone who entered the property and stayed with the owner's permission.  Now that this permission has been revoked, the legal way to remove them is to file for an "unlawful detainer" (i.e. eviction). Typically, a written 30 day notice must first be given.  If they still do not vacate at the end of that time you will need to file suit in court.  Until things are legally resolved, do not be tempted to use self-help measures such as removing their belongings and/or changing the locks.  If you do you could find yourself on the wrong side of a lawsuit.