Stay away from anything that's water damaged or been repaired for water damage. You can replace the frig or ac or water heater but you cant make it how it should be if it has water damage.
Make it your number one goal to avoid water damage. Just move on and find one that's ok. I have also noticed people talking about sagging rear walls or floors in toy haulers because of the large cavity effect in the rear. I dont know what brand or models but I did notice it on line so it may be an issue that you will want to research more.
I can understand how this may be an issue with the large "box" back there. In a regular RV style the inner walls help to provide a stronger "honeycomb" effect and make it more rigid. Good luck to you and be very careful.