Around the world, the Airbnb marketplace provides opportunities for property owners to bring in extra, semi-passive income. These folks can earn thousands of dollars per month simply by renting out their spare rooms or other livable properties; however, hosts also need to implement certain measures to make sure everything runs smoothly.

Part of this work involves setting up ground rules for guests who are staying over. These guidelines typically center around how travelers should conduct themselves while on the property. As guests search various Airbnb accommodations, they get to view each set of rules under the "house manual" and "house rules" sections.

Hosts who want to be extra vigilant can even turn off the instant booking feature for their property. Without instant booking, guests first request to stay at a property for a given period of time; from here, the host has up to 24 hours to approve or deny the request before it automatically expires.

With that in mind, some Airbnb hosts are providing insight into what makes them turn down certain bookings from guests.

What every traveler who uses Airbnb should know

Previous reviews from other hosts make a huge difference.

If an Airbnb host sees that someone with a slew of bad reviews requested to rent out their space, they may be more inclined to say no. Ultimately, most property owners don't want to run the risk of dealing with guests who don't respect the space, break house rules, etc.

Sometimes, hosts even go the extra mile of reviewing social media feeds, especially when they feel someone's stay could cause difficulties. When these concerns arise, looking at a traveler's social media pages often provides insight into why they want to rent the space.

One Airbnb host told CNBC that upon noticing a traveler (who lacked Airbnb reviews from previous hosts) requested a stay at her property, she scanned their Facebook feed. Eventually, she ended up declining the requested stay when she saw the traveler intended to throw a party at her property.

At the end of the day, most people renting out property on Airbnb aren't trying to give travelers a hard time. They just want to ensure they're only taking bookings from respectful guests who won't cause problems.