It's no surprise that younger generations tend to shop online more than older generations do -- even for houses. According to a Zillow Group (Z -1.45%) (ZG -1.27%) survey, an astounding 59% of millennials said they'd be at least somewhat confident making an offer on a home they saw only virtually.

That's understandable because people can still back out before signing a contract. But making an offer after only viewing the home online can secure a deal, a practice popular in a seller's market like the one we have now.

Though it seems inconceivable, Zillow's research found that 39% of millennials said they'd be OK with actually buying a home they saw only online, which can be risky. A tragic (and extreme) case happened last month when a disgruntled 84-year-old homebuyer killed his real estate agent upon first visiting the house he had just purchased sight unseen.

That example aside, the point is this: What you see online isn't always what you get. Neither pictures nor even videos tell the whole story.

2 people and dog online shopping


1. The home's smell

You can't tell through photos and 3D virtual walkthroughs what the house and neighborhood smell like. A stench that would normally send you running to the next available property -- such as lingering pet odors or the aroma of a waste-treatment plant -- can't be determined when shopping online. You can solve this problem by asking your real estate agent to screen for foul odors.

2. Noises in and around the home

Noises fall under the same category as smells. You could be bombarded with a perennial noise problem that you wouldn't know about from only having a virtual viewing. A dog barking daily outside your window or a train that blows its horn at a nearby grade crossing could be deal-breakers, but only if you can hear them.

3. The HVAC system

Usually, if there's no mention of the heating, ventilation and air-conditioning (HVAC) system in the listing, you can assume there's a unit that's old and on its last legs. There's an easy remedy for this one. Just have your agent look. The date of the equipment is typically visible somewhere. If not, your agent can ask the homeowner for you. The same goes for the water heater. A worn-out HVAC unit or water heater might not be a reason to call off a deal, and old units can usually be used by the buyer to negotiate a modest price break or to get seller concessions at closing.

4. The neighborhood

The good news about virtual homebuying is that you can get a good feel for the neighborhood by searching online maps. You can see where the home is located in relation to other amenities, such as shopping, restaurants, hospitals, schools and parks. You can even find out how long your commute will be by using an online map to select the locations and the times you'll be driving. What you won't get is a feel for the life (or lack thereof) of a neighborhood unless you visit it yourself.

If you must buy a home after only seeing it on Zillow

There are some precautions homebuyers who wish to buy virtually can take. It's imperative to have an inspection contingency as part of the offer (and then to actually get the home inspected). In addition, if you know someone in the area, ask them to tour the home while conducting a live video chat with you. Have your real estate agent ask the seller about home features, such as the type and age of the appliances and roof. Also, if the homeowner made any renovations, have your agent make sure they comply with local building codes.