Security is a concern for sure. Nice thing about this property though is it is at the end of a dead end road that has only two houses on it and the driveway is off of that. Unless you knew it was there, 99% of people wouldn't even think about it when driving by.
I am also considering having a caretaker stay on the place to keep an eye on things and keep the brush down in exchange for a cheap or free place to live. Problem with that is needing them to be fully self contained since I don't have power, water or septic (power and water are at the corner of the lot however) so it would take the right person to want to "rough" it a little.
Other option is getting some security cameras setup to record what is happening. Not as much of a deterrent as someone living there but better than nothing. Also better for peace of mind being able to take a look at the state of the 5th wheel at any time remotely should I have a concern. Logistical issues of course for Internet but maybe Elon will solve that for me...