A historic flat a block from the Seine in Paris’ St. Germain neighborhood. A cottage perched on an Irish cliff. Countless oceanfront condos. Using websites like Airbnb, HomeAway, and VRBO (Vacation Rental by Owner), you can rent a spare room or an entire property in digs and destinations as diverse as your travel dreams. But how to get a good deal and avoid trouble? Here’s how to rent sans regrets.

Know What You Want

Airbnb offers more than 3 million listings worldwide, from a shared room in Detroit to a 12-bed French chateau; VRBO and HomeAway, which are owned by the same company, also boast zillions of places. A key difference: VRBO and HomeAway list only full-time vacation properties; Airbnb has both full-time rentals and spare rooms (or beds) in hosts’ homes.

It’s easy to get mired in endless options—especially if you’re traveling to a big city—so use the sites’ filters and maps to zero in on exactly what you want. A crash pad close to your business meeting in midtown Manhattan? An oceanfront house that sleeps 30 in Aruba? Then expand your search if you can’t find it or want additional competing choices.

Make a budget, knowing that larger groups often get better deals. For example, for a November weekend in Rome, Italy, we found a four-bedroom apartment sleeping 10 for $429 a night, including fees and taxes (around $43 per person); most four-star Rome hotel rooms run at least $123 a night for double occupancy that time of year.

If you’ve never rented a vacation home, know that you won’t have a concierge, room service, and other amenities. Plus locating and checking in and out of a hotel is usually easier than coordinating with a rental landlord.

Look Closely at the Listing

Scrutinize images of your possible temporary home. Do they show the neighborhood, street, building exterior, and interiors? (Too few photos can be a red flag.) In that listing for a two-bedroom, do you spy two boudoirs? Or is the landlord counting a den with a sleeper sofa as a second bedroom? Does the place look clean? Are the pics carefully shot?

If a feature is important to you (a balcony, a coffeemaker) look for it in the images; you don’t want to dream of lounging on a riverside perch only to discover the apartment faces a wall, not the Nile. Check the map. How close is the pad to what you want to see or do? Are there nearby restaurants? Is it convenient to public transportation? Is there free parking?

Review the Reviews

All of the big rental sites let customers rate stays and hosts on a one- to five-star system. In general, a lot of positive reviews may indicate you aren’t leasing a dump from a weirdo. But read them carefully and be skeptical. It’s fairly easy for landlords to fake-rent their own properties and post glowing reviews. And all three sites let both renters and listers review each other, a two-way marketplace that means guests might not submit negative ratings for fear of getting dinged by the host.

If you have multiple choices, seek out properties with numerous, mostly positive customer reviews. But know that newly listed properties can cost less as landlords try to build positive feedback. When reading reviews, look for specific problems (a less-than-comfy bed, noise). And don’t be shy: Sites let you submit questions directly to landlords.

Get a Good Deal

Being flexible as you search for a vacation rental increases your options and uncovers additional deals. Renting via Airbnb, HomeAway, and VRBO often—but not always—costs less than a hotel. Groups in particular usually will save a lot by renting a large home rather than multiple hotel rooms. Some examples of deals we quickly found:

  • An Architectural Digest-worthy one-bedroom apartment in Paris’ hip Marais neighborhood rents for a three-day weekend for $230 a night ($843 total, including all fees and taxes). In the same neighborhood, the four-star Les Jardins du Marais hotel offers classic rooms with kitchenettes (and tight quarters) for $479 a night (grand total of $1,597 for the weekend with all taxes and fees)—nearly twice the price of the chic pied-à-terre.
  • Take the fam skiing in Aspen in mid-February and pay $479 a night at the Westin Snowmass Resort for a room sleeping four ($2,221 total for three nights, after taxes and surcharges). The ski-in/ski-out hotel is nice, but for far less you can rent a spacious, renovated two-bedroom condo within walking distance from a lift—it’s $275 a night, $1,513 all in, a savings of 32 percent over the resort.
  • For a week in September in Tokyo’s desirable Shinjuku neighborhood, we could stay at the Hyatt Regency for $181 a night ($1,531 total, including taxes and surcharges). Option two? An apartment across the park from the hotel for one-third the price—$62 a night ($547 total). Though it sleeps four, the pad is small, but so are rooms at the Hyatt, which only allow two guests.

Many landlords, particularly on Airbnb, offer discounts for longer stays. We also often dug up good deals offered by hosts with newly listed properties that lack lots of reviews; these owners use discounts to book their pads to build up positive reviews.

Watch for Hidden Fees

It’s annoying that none of the big three booking sites list in its search results total prices including cleaning, management, and other fees. For example, we found a hip two-bedroom condo in Austin, Texas, advertised at $225 per night, or $450 for two nights. Yippee! Wait, nope. Click on the listing details and the price jumps to $1,000 for two nights—more than double the advertised rate—when you add in a cleaning fee, Airbnb’s service fee, and an occupancy tax.

Yo, hotel booking sites! You, too, need to get your acts together and disclose total costs upfront.

Book Ahead (or Instant Book)

In peak season, rentals in popular destinations go quickly. Unfortunately, many landlords are lousy at updating availability. You’ll find an ideal place, reserve it, and after several hours or even a day get a “Sorry, we’re booked” email. Sometimes, it’s worse: You wait a day for the site to tell you that, since the owner didn’t confirm, you have to start over. Our editor wasted weeks on such a search/request/refuse/search-again merry-go-round trying to rent a flat in London in July.

If you can, book far ahead. Having trouble securing a spot? Limit your search to “instant book” listings, which let you reserve and pay right then, no waiting for an owner or property manager to confirm and complete (or decline) the deal.

Check the Cancellation Policy

The three sites let hosts have different kinds of cancellation policies. Airbnbers, for example, can have flexible policies (cancel up until a day prior to arrival for a full refund), moderate (cancel with full refund up until five days prior to arrival), or strict (cancel up until one week prior to arrival, but get only a 50 percent refund). If you’re booking far ahead, look for flexible or moderate refund policies.

Play It Safe

With HomeAway and VRBO, you get a full-time vacation home, meaning it has owners, but they won’t be staying with you. With Airbnb, you could bed down in a room at someone’s occupied Paris condo, a basement flat in a D.C. rowhouse, or a shared bunk room in a Prague hostel. If you’re sharing digs with a stranger, reviews become very important.

When searching on Airbnb, if you don’t want to have new temporary roomies, narrow your listings to “Entire home.” Airbnb also offers hosts the chance to either list references or obtain a “Verified ID” status. But the latter just means they’ve submitted to the site a government ID, phone number, or other form of identification. Airbnb “Superhosts,” however, have hosted 10 or more bookings, received five-star ratings at least 80 percent of the time, responded to messages within 24 hours at least 90 percent of the time, and completed all confirmed reservations without canceling.

All sites require third-party payment (pay the website, not the rental owner). Avoid scams by refusing to give anyone funds outside of that structure. Requests for cash advances or wire transfers are big red flags. (All communication with your host should flow through that system as well.) Airbnb, HomeAway, and VRBO all offer protections against fraud and uninhabitable rooms. And if there’s a problem the booking site won’t make right, the Fair Credit Billing Act and your credit card company will allow you to dispute the charges.

Consider the Consequences

Renting a vacation home can have an impact beyond your little stay. In many cities so many properties have been converted from residential to vacation spots that rental-housing shortages exist for middle-to-lower-income residents. So while we love the choices and deals offered by vacation rental sites, it’s important to recognize that there are well-justified concerns over how these arrangements affect cities’ full-time residents.