I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
You have the ability to serve them with a 14 day notice to pay the rent owed or vacate the premises. Then, if they do not pay, you can take them to court and get an eviction. If they choose to move out instead, you'll be able to apply the security deposit to the rent they owe you. You should know that if you wind up filing a lawsuit, they'll be allowed to stay as long as they pay in full at any time before the trial. With luck, they'll be willing to pay once you serve the notice and there won't be any more problems.
The notice can be served either by having a third party hand a copy to the tenant personally (preferably someone who will come to court and testify to doing so, if necessary), or you can mail to the property. Frequently, when it's mailed, landlords will also post a copy of the notice on the front door. Another option is to send via certified mail, so you have proof they received it.
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