If buying used, have a good look at what is new now. Look at the quality builders in particular. Much better to buy a well built used than same money for new junk.
Research, research, research. Don't be buying a mistake that you won't be happy with in a few years. Mistakes cost money. Big money.
JMO but a 30' 5er is going to get small on you if you are going to fulltime or do multi month trips. Go over 35-36' then you are getting too big for some of the nicest parks, the State parks & National Park CG.
Last, make sure that 'she who must be obeyed' has a decent sized galley area to work on or you will be spending a fortune in restaurants.