I have hosted 130 sets of guests and most of them never had a review -- we are their first Airbnb stay. Do not let zero reviews scare you...we've had great experiences with our guests. We are in-home hosts so that tends to weed out most rascals, but even if we weren't I'd take a new guests. You can ask questions, and get other documentation, and get a good feel for what they are like. If you don't feel like you can screen well, then hire a company to do that part.