You cannot violently throw a tenant out of their apartment, because that is a violent crime. You can violently repel an intruder in self-defense, but if you have actually rented an apartment to someone, they are not an intruder. If, after first renting to them, you later believe they should leave—and they disagree—then you have a dispute about the terms and duration of rental. (It might be a really one-sided dispute in which one side is clearly in the right, but it's still a civil dispute.)
If their previously lawful residence has become unlawful (e.g. as a result of a failure to pay rent, becoming a nuisance, exceeding an agreed duration, etc.), in that case you proceed in a peaceful, legal fashion: you first give them formal notice that they are required to vacate the property; and if they fail to do so, you get a court order instructing the police or sheriff to remove them. The precise series of steps, and how many days they have to respond, varies by country and state/province (and may also depend on length of occupancy, usually shorter-term tenants being given fewer protections). You cannot yourself adjudicate and enforce the dispute, because vigilante justice is disfavored in most civilized countries. If, say, a client failed to pay your contracting bill for a job they owe you money for, you cannot walk into their cafeteria with a baseball bat, threaten the cashier, and seize the money that is legitimately yours. Instead you have to sue them in court, get a judgment, and then have the judgment enforced. There are ways you are allowed to enforce your legitimate claim, and ways that are... not allowed.
See the previous coverage for the long version, but the tl;dr is that renters that rent for more than 30 days are protected as tenants by California law, including (normally proper) long drawn-out eviction proceedings.
No, not if that was not under the original terms of the lease. You may own the building but in the eyes of the law it is the tenant's home and you can't throw them out onto the streets without due process.
If their previously lawful residence has become unlawful (e.g. as a result of a failure to pay rent, becoming a nuisance, exceeding an agreed duration, etc.), in that case you proceed in a peaceful, legal fashion: you first give them formal notice that they are required to vacate the property; and if they fail to do so, you get a court order instructing the police or sheriff to remove them. The precise series of steps, and how many days they have to respond, varies by country and state/province (and may also depend on length of occupancy, usually shorter-term tenants being given fewer protections). You cannot yourself adjudicate and enforce the dispute, because vigilante justice is disfavored in most civilized countries. If, say, a client failed to pay your contracting bill for a job they owe you money for, you cannot walk into their cafeteria with a baseball bat, threaten the cashier, and seize the money that is legitimately yours. Instead you have to sue them in court, get a judgment, and then have the judgment enforced. There are ways you are allowed to enforce your legitimate claim, and ways that are... not allowed.