6 ways to use your kid's old bedroom

Host a couch surfer

Not ready for a roommate but looking for a little adventure?

Sign up to host global travelers looking for a place to stay in your town. Some online matchmaking sites, like Servas.org or Couchsurfing.org, don’t allow you to charge. Instead, you reap cultural rewards from meeting foreign travelers.

Airbnb.com, meanwhile, lets you put your guest room out there as a rental, which can be lucrative if your zoning allows it and you live in a major city.

Estimated earnings: It depends. In Chicago and its suburbs, for example, we found rooms for rent on Airbnb starting at $45 a night. Dozens of spaces were offered for more than $100 a night.

The site offers help on estimating what your room might be worth.

Airbnb will charge you 3% of your rental fee for each booking.