and there are surprises.

Good surprises, such as the one Ana O'Reilly encountered when she checked into a villa in Palm Springs, Calif., are rare. She was dumbstruck to discover the home looked better than the pictures in the listing, which was a first. The refrigerator was stocked with champagne and bottled water, and bowls of M&M's were left in the kitchen as a welcome snack.

"It was incredible," says O'Reilly, a marketing executive based in London.

And there are the not-so-good ones, such as  the one encountered by Timothy Trudeau when he rented a home in Santa Barbara, Calif., with his family. After getting settled, he decided to take a dip in the pool.

"As we were floating around, I started to notice that the property had small infrared cameras mounted all over the place," recalls Trudeau, who runs a music industry website in Lemon Grove, Calif. "Suddenly, we went from thinking we had our own little private slice of heaven to thinking we may be starring in some kind of Web reality show that we were unaware of. Super creepy!"

Good or bad, you can expect surprises during your next vacation rental, because, well, it's a vacation rental. There are no real standards, as many renters are discovering. One in five Americans stayed in a rental last year, up 27% from 2014, according to a recent survey by Travel Tech, a trade group.

For every villa that exceeds expectations, there's a little shop of reality TV horrors, although Trudeau admits he hasn't seen any closed-circuit footage of his family vacation online. Companies such as Airbnb close a new round of financing every other week and HomeAway was acquired by Expedia. It seems the vacation rental industry is poised for another year of major growth. Half of all Americans say they expect to book a short-term rental.

How do you make sure you get more good surprises and fewer unpleasant ones? It's a combination of renting from a trusted source and due diligence. It doesn't take long, and the rewards can be great. For someone such as Trudeau, who travels with his family, the savings from a vacation rental can be considerable  compared with a hotel.

Doing your homework is essential. It involves combing through user-generated reviews, scoping out the property on your favorite mapping site and interviewing the owner — by phone, preferably. If you live nearby, an in-person visit is a must. A reputable owner will let you have a look at the property if it's unoccupied.

What if you live far away? That's the idea behind WeGoLook, a service that will independently verify the property's ownership and neighborhood. The company dispatches what it calls a "looker" to take new pictures of the property, street views and neighborhood views, and that person is available to answer questions. Robin Smith, WeGoLook's CEO, says people usually turn to her inspection service, which costs $69 per report, after a rental problem. Most memorably, one customer came to WeGoLook after renting a property that had a pool without water.

There's no substitute for on-the-ground intelligence, Smith says, "especially when you're sending large deposits that can be lost."

Another service that helps you avoid surprises with a "by-owner" rental property is Pillow (pillowhomes.com). Pillow screens the properties it manages, sending a supervisor to interview the owner and ensure the property meets its standards. Those include curtains, kitchen supplies and enough utensils for the maximum number of allowed guests and enough pillows and blankets for each sleeping surface. You can find Pillow listings through HomeAway (homeaway.com/pm/Pillow-740813w). "Pillow validates the property for guests," says Sean Conway, Pillow's CEO.

VaycayHero (vaycayhero.com) promises to help avoid surprises by adding another layer of service: a 24-hour concierge who can mediate any issues between travelers and vacation rental hosts. Among its successes is salvaging one customer's vacation rental on Hawaii's Big Island that didn't have wireless Internet access, which it turns out was a deal-breaker for the guest. VaycayHero's concierge team quickly arranged for a wireless Internet connection to be installed.

How about the professionally managed vacation rentals? There are differences there, too. Companies offer guarantees and promises that the only surprises you'll find will be positive ones. Wyndham's Vacation rental bill of rights, for example, promises a guest service team to assist with questions you may have during the booking period, around-the-clock maintenance assistance during your stay and access to local representatives "with expertise and knowledge."

The implication is clear: You have the right to a surprise-free rental — specifically, a rental without any negative surprises.

In an industry that has precious few standards, it's nice to know someone cares that you're having the rental experience you paid for.

How to avoid a negative surprise when you rent

• Rent with names you trust. Airbnb, VRBO and FlipKey have legitimate rentals and higher standards, says Andrew McConnell, co-founder and CEO of Rented, a vacation rental marketplace. "Stick to trusted and verified brands," he advises. "It's your best bet for avoiding unpleasant surprises."

• Assume nothing. Every vacation rental comes with linens, right? Wrong. Ryan Lockhart discovered that when he rented a house in North Carolina. When he checked in — surprise! — no linens! "I had to drive 45 minutes each way to buy linens from Walmart, which we had to wash and dry before we could even sleep," remembers Lockhart, who owns a digital marketing agency in Bluffton, S.C.

• Never wire money. "Do not pay for a vacation rental with cash, money orders, Western Union or other money transferring services," advises Isaac Gabriel, founder of the online timeshare rental portal EZ Resort Vacations. Wiring money can lead to the most unpleasant surprise of all: a rental that doesn't even exist.

Christopher Elliott is a consumer advocate and editor at large for National Geographic Traveler. Contact him at chris@elliott.org or visit elliott.org.