@John5659 I honestly can't recommend Airbnb as a platform for long-term bookings, for so many reasons. They don't vet guests in any useful way, nor let hosts access enough data to do a background check. The "security deposit" you specify in your listing doesn't actually exist - they don't hold or charge anything. They only collect the first 30 days rent upfront, and if a subsequent payment fails, Airbnb washes its hands of the booking.
Your request might have been genuine, but there's never a guarantee that the person is who he says he is. New listings like yours are the ones most frequently targeted by scammers and squatters, which are rampant these days. I'd strongly recommend sticking to short bookings while you're learning the ropes - that way, in a few months you can quickly rack up lots of reviews, build an established reputation, and then raise your prices and refine your parameters accordingly.
Even so, if this offer just sounds too good to pass up, you can offer the guest a short-term trial period via Airbnb, and if it's successful you might consider organizing a lease agreement off-platform with a real deposit.