It sounds an excellent idea to me, since it gives a young person a degree of independence while allowing their parent(s) not to worry as much as they would if their offspring had completely deserted the family home.
However caravans can be very cold and damp this time of the year (and cost a fortune to heat). Additionally you might need planning permission. See my post here:
http://www.theanswerb...n/Question224524.html
(If you look at the second link I've given, please click 'Previous section' at the top of the page to start reading from the beginning of the report).
Chris