Upvote:3
Most of the tips for avoiding theft for RVs would be very similar to advice for cars. While you are certainly more of a target you also have one significant advantage in that it is easy to keep a potential thief guessing on if there is a person in the RV. We often hung a large blanket between the cab and house sections of the RV both for privacy and so it was tough to tell if we were in the RV or not. The important thing then is to just not leave anything visible in the cab.
Also, give RV parks a shot. We stayed in forests, parking-lots, driveways and all sorts of places on our long trip. RV parks have power, internet and since many people use them for tourism they can often have good access to city centers. Don't expect that you are much more safe in an RV park though. Lock up and hide your valuables.