Airbnb has radically transformed the hotel industry, making it easy and often cheaper to book accommodations. Millions of people have used the service so far, but there are a few things you should know before you reserve anything through the site.

1. Airbnb will pay for hosts to have professional photos taken
Hosts can apply to have Airbnb’s photographers take pictures of their rental space. “Airbnb has put a lot of effort into improving the quality of photos on a listing,” says Scott Shatford, founder of Airdna, a site that offers data and insights on the home-sharing economy. “It makes a huge impact on bookings, but it also verifies that the place being booked is actually the place being advertised.” (You can tell if a listing has taken advantage of the service because of the telltale official watermark on the photos.)

These pictures have pros and cons for travelers. They can give a rental home credibility—a plus for nervous travelers—but they can also make the space look better than it actually is. Just keep in mind that photos can look somewhat better than the reality, and make sure to really study the written description, as well as reviewers’ comments and ratings.

2. Airbnb isn’t always cheaper than a hotel
Airbnb can save you some money, but it’s not always the cheapest option, says Dany Papineau, who created Airbnb Secrets, an online resource designed to help hosts and guests become Airbnb pros. It pays to take all of the extra costs associated with an Airbnb rental into consideration: You’ll owe a service charge, typically 6% to 12%, when you book a room (it varies depending on the length of stay and the number of guests you’re traveling with). In addition, hosts can add a one-time cleaning fee and a security deposit charge to the overall cost of rent.

Plus, Airbnb rentals in cities like New York City, San Francisco and Portland can come with extra taxes on top of the rental price tag, says Papineau. “Airbnb has a lot of agreements with many cities around the world to start to collect short-term taxes.” Once you do the math on the additional fees, a hotel room may be cheaper for a short-term rental.

Read more: Use a ‘Fake’ Location to Get Cheaper Plane Tickets

3. You can get scammed if you communicate with the host outside of Airbnb’s site
To keep hosts and renters safe, Airbnb requests that all communications take place through their platform. (Papineau says he’s heard horror stories about people taking advantage of Airbnb naiveté to scam people.)

Communicating through Airbnb’s messaging system is the only way the company can ensure you get what you’re paying for—and it’s also the only way it can stay in business since Airbnb charges hosts a fee on every reservation. So while you’ll find it difficult to communicate with a host off of the site (Airbnb intentionally makes it hard to exchange phone numbers or email addresses), you probably don’t want to anyway.

4. Airbnb doesn’t conduct background checks on guests or hosts
“There is not a traditional background check,” says Shatford, who recommends paying close attention to reviews.

“Filter searches for properties that have had successful five-star reviews in the past,” he says, also suggesting that guests look for listings with a Verified ID (which means Airbnb has scanned an official ID, such as a driver’s license or passport, and has asked users to provide verified contact information, like an email address or phone number). “That way, if anything does go wrong, they can track the person down,” says Shatford.

Read more: 29 Travel Hacks Even Frequent Fliers Don’t Know

5. Airbnb will help if you don’t feel safe
If for any reason you don’t feel comfortable when you arrive at a place you’ve booked on Airbnb—or it’s not as advertised—Shatford recommends calling the company’s customer-service line at (415) 800-5959.

“Their customer service is really good with safety concerns,” he says. “They typically go out of their way to figure out other lodging or another Airbnb property, getting you somewhere else quickly if you feel unsafe.”

6. Cancellation policies vary drastically
Unlike hotels, which let guests pay upon arrival and have flexible cancellation policies, the majority of Airbnb hosts require a security deposit and set their own cancellation policies, which vary in severity, says Shatford. “Even if you cancel a year in advance, you may only get a 50% refund.”

And while some fees, like the cleaning charge, will be refunded to you, Airbnb’s service fee is non-refundable unless it’s the host who decides to cancel. In short, it’s a good idea to read all of the fine print before you book.

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