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When renters sign a lease to move into an apartment, they often fork over more than just one month's rent. Most landlords also charge a security deposit -- an amount to cover any repairs or cleaning that may be required once the tenant moves out. Still, renters often wonder: What happens with this chunk of money once they fork it over, and when will they ever see it again? Here are the answers to renters' most common questions -- and advice on what to do to make sure you get it all back.

Q: Why do I need to put down a security deposit?

Quite simply, it's a guarantee that you're going to take care of the property you're renting. Normal wear and tear is to be expected, but if your new puppy chews through the screen door, or your muddy hiking boots permanently stain the carpet, your landlord needs a way to cover the cost of cleaning, repairs, or replacements. Owe back rent or late fees when you move out? That could come out of your deposit too.

Q: How much is a security deposit on average?

Every state allows landlords to charge a security deposit, but the amount varies. In some states, limits are as low as $100, while others are allowed to ask for several months' rent. Some states have no limits on how much you can be charged, so make sure you have cash saved up when you fill out that rental application. Check this list of security deposit requirements by state to see how much yours will set you back.

Q: What does my landlord do with my security deposit?

Generally speaking, landlords are required by law to put a security deposit into a bank account that's separate from their personal funds. (Check your lease; this info could be detailed in all the legalese you skimmed over to get to your signature.) And if your deposit earns interest? In some states, you're entitled to it once you move out. In other parts of the country, your landlord can keep it as part of an "administrative fee."

Q: What are some reasons money could be taken out of my security deposit?

Think of it this way: Your landlord is in charge of updating anything in the property that wears out over time. But "if you damage the property, repairs are your responsibility," says David Hryck, a lawyer specializing in real estate and a partner at Reed Smith in New York City. That means if your kiddo finger paints the walls or you accidentally crack a tile in the bathroom, the cost of repair will come out of your deposit. Even if a guest of yours breaks something, you're the one who'll be expected to pay.

Q: When will my deposit be returned?

This also depends on where you live: Tennessee has no hard-and-fast deadline for security deposit returns; New York only requires that deposits be returned within "a reasonable time," whatever that means. But in most cases, your landlord needs to return your full deposit (and possibly interest) within 14 to 60 days after your lease expires. If you don't get all your money back, then you're entitled to receive an explanation of how an amount was used for cleaning, repairs, back rent, or late fees.

Q: What can I do to make sure I get it back?

As soon as you get the keys to your new place, complete a "move-in inspection form" that you and your landlord both sign.

Make sure you also take pictures, focusing on any pre-existing damage, advises Michael Vraa, the managing attorney and hotline director for HOME Line, a nonprofit tenant advocacy group in Minneapolis, MN.

Then, on your last day in the property, take photos again to prove that the place still looks good on the way out. Hone in on typically troublesome areas like the oven and refrigerator to show that they're clean as well, Vraa adds. Then ask your landlord to walk through the rental with you and point out any issues you should resolve before you leave.

Q: What if my landlord doesn't return my security deposit?

First, make sure he has your new address and knows where to send your deposit. You should also send a letter requesting your the return of your security deposit. (This is actually required in some states.) If your landlord still ignores you, then you have the right to take the issue to small claims court. "In some states, if the court finds that your landlord has intentionally broken the law by not giving you back the deposit, you may be awarded a sum larger than your original security deposit," says Hryck.

Neal Leitereg and Tasha Schroeder contributed to this post.