I have used Airbnb a couple of times and have had good experiences. ^^

For cost, you should plan on 6-12% on top of the rate per night you see posted on each listing. There are no other 'hidden' costs. Since you know about that fee, you can plan for it when you are looking for places within your budget. You also have the opportunity to confirm the booking (and can see what the actual total amount is, including the fee) before you submit your payment.

My advice is to look at lots of different options and when you find something you want, reach out to the host by sending them a message. In my experience, the hosts with lots of reviews (meaning they have hosted many times) will reply to you very quickly. Also read the reviews of past guests. For me, this part isn't unlike reading reviews found on TripAdvisor or other travel sites.

What other problems are you concerned about?