Bet you probably wouldn't think to check here.

The hunt for the perfect apartment can sometimes feel like a never-ending search for the impossible. You’re constantly glued to a million different apartment-finder apps, and meticulously compare neighborhoods and rent rates and square footage in your spare time. And then—if you’re lucky, and no one scoops it up first—comes the tour; when you finally get to poke around IRL and see just how much those online listings stack up to the real thing.

Of course, if you’re like most newbie renters, you may inevitably overlook some things on your initial walk-through. But according to Caroline Bass, an associate broker at Citi Habitats, there are a few things you should definitely be aware of before signing on the dotted line and handing over that rent check.

Aside from the usual suspects—like closet space, counter space, and whether or not there’s laundry in the building, Bass has one other trick in particular she suggests clients pay close attention to—and chances are, it’s not one you’ve even thought about before.

“My favorite piece of advice to renters is to check out the basement of a building,” says Bass. “If the basement is poorly maintained, it’s usually an indication that the building isn’t well maintained.”

As for what exactly you should keep your eyes peeled for, Bass says, “If you see glue traps or any critters running around down there, keep on searching!”

Another pro tip? “Check out the apartment at different times of the day,” says Bass. “If you see an apartment during daytime hours, go back and see what the neighborhood is like at night or after work to make sure it’s a good fit for you.” If you’re looking for a quiet neighborhood vibe, and notice things get rowdier than you’d like them to after dark, that might be a sign this block just isn’t for you. Same thing goes if you love a neighborhood with a plenty of nightlife—if the area’s just too sleepy, you may want to look elsewhere.