Hi @Cindy84 It's very appropriate to ask for a security deposit - you can add that under Pricing settings. It's not collected by Airbnb but if high enough, may act as a deterent & give you some additional leverage if you have to make a claim for damage.
I'd recommend you find someone nearby to act as host on your behalf - to check the guest in, answer any questions, and be there for check out. Leaving your place completely in the hands of a stranger while you're not in the country seems very risky to me. As well, if you're travelling, you may not be able to respond to your guest in a timely manner, or solve any problems he may have - what if the plumbing breaks down, or a major appliance, or any number of things that can go wrong? You really need to have a co-host in your situation. Hope that helps - Karen