It is not easy to find a good used rv at a reasonable cost, but it is also not impossible. You are in a good area--Las Vegas has a ton of dealers, Phoenix is not too far away and there are usually a lot for sale on CR in that town, plus we bought ours in Tucson.
Retired lifestyles especially can change quickly through illness or moving from a starter smaller RV to something larger--also the opposite. So places where people retire, like Florida, Texas and Arizona and to a lesser extent Nevada, Utah, etc. are good hunting grounds.
There is a lot to say for a Lazy Daze and I looked for one, but settled for a Winnebago that has been great for just two of us along with grandkids sometimes. The parents will join us but sleep in a tent. They like getting away...:)
With our jackknife couch and fold down dinette across from each other we can make one big bed by using foldable tables in between and cushioning that with pillows and a comfort camping rollup self inflating air mattress (I'm being specific because I hate those inflatable air mattresses!) Then it is a huge sleeping area that can easily fit two kids and two adults. Plus the cabover bed for two more. So we have more room than most small RV's just because of the layout.
I wouldn't look at anything older than 2005 right now and expect to pay at least in the high $20,000 range. If you are looking at something in the early 2000's you could stay under your limit but you would expect more damage and appliances with less life in them.
The only thing I can think of that you can't easily add is an oven. Newer RV's often don't have ovens, just convection microwaves and stove tops. With a family you might want one.