I'll just add if you are buying used and an older model think leaf springs. Leaf springs are metal and metal "fatigues". Especially on the 31 ft with all that length/weight behind the real axle.
I think a lot of RV'ers overlook this aspect and importance of ride with a MH.
I put new leaf springs and 'added' one leaf. Ahhhh what a difference, if you want to bump up the limo ride experience in a MH. Also added new Monroe RV shocks and we were on our way across the country in style, comfort and ride-ability. :C