Where most of us may see an empty bedroom, homeowners around the country are seeing new ways to make big bucks by renting out those rooms, for an average of $65 per night, to vacationers.

Families like the Norries, from Montclair, N.J., are listing their spare rooms on rental websites like Airbnb.comor iStopOver.com, which help you to rent a room in your home for short periods, to make some extra cash. Postings on Airbnb.com have doubled in the past year, according to the site. They now have 70,000 active listings in the United States, up from 35,000 at the beginning of 2012.

These sites find you the renters and help you vet tenants' trustworthiness by setting up phone calls between buyer and seller. They also give you insurance, all free of charge.

(ABC News)

Nearly all of the Norries' neighbors are doing it, earning an average of $6,000 a year. For the Norrie family, that $6,000 could be the difference between staying in their home or having to sell.

"We hope to be able to keep our house. Because we're very underwater as a lot of people are," Mia Norrie said. "We're trying to stay here because we love our house."

Interior designer Cathy Hobbs says there are five easy tricks to transforming any room into a rentable oasis. The Norrie family spent a total of $239 using these tips to improve their spare room. Appraisers say they could make $12,552 on their extra room this year alone.

Tip 1: Clear out the clutter. That includes family photos and personal touches.

Tip 2: Paint makes rooms feel bigger, so skip the plain, boring white. Hobbs said if you're going to spend any money redoing a room for rent, spend it on paint.

Tip 3: Big beds sell better. Hobbs says queen beds are going to open up your rentable rooms to many more potential guests. It's also a good idea to get new sheets to make the room feel cleaner and fresher.

Tip 4: Get free professional photos of your rooms for rent. Home rental sits like Airbnb.com will even send a professional photographer to your home to take photographs, for free.

Tip 5: Use secret search terms when listing rooms. If you live near a big city, park or lake, don't be afraid to brag about it. It'll put your listing at the top of search results. The professionals say never use words like "cheap," "bargain" or "budget." The price is listed and speaks for itself and renters might associate those words with poor quality. Instead, describe home the room will feel such as "private," "luxurious" or "a treasure."

Before you start accepting bookings, make sure you know your local laws for short-term rentals. These laws can vary greatly from city to city, so check with a local expert to see if you need certain permissions. It's also a good idea to check with your insurance company to make sure you're covered in case of an accident.