I have a furnished second bedroom that I list on airbnb. I decline most requests, but now and then will have a guest. I need to be 100% sure about the person before inviting them into my home.
Still kind of new at this, but my first guest was a UCLA professor that was in town for a conference. Second was a music producer from Germany who was in town working on a project. Both provided their links to LinkedIn and Facebook and were great experiences.
Last guy I declined was from Italy. Didn't state his profession, no real insight into who he was, and he told me he'd have a guest with him on "some nights". Didn't exactly give me any confidence so I said "no".
Fortunately I don't really need the extra money, but it's nice to have some extra dough drop in my bank account on occasion, and it also provides an opportunity to meet some cool people. If you have the space, I'd say go for it. Just be careful about who you take in!