I through bolted {quarter inch bolts, large flat washers and double nuts} a small Sentry safe into the bottom of my closet. A bad guy would have to have some serious tools and more time than most thieves allocate to get in or it out.
It has a minimal fire rating and even a safe with a full 30 minute burn time rating is probably toast in an RV fire. First of all it will take probably most of that time just to get the fire department on scene. RV fires, typically alongside the highway, rarely leave much other than the carcas of the chassis.
Having the safe enables me to store cash, credit cards, cameras, phones and firearms safely/securly with nearly instant access as needed. About $100 for the safe and another $10 for the mounting hardware.
:C