Yeah, the timing part is tough to even generalize. Everyone suggests that you find a floor plan that works for you and a coach that has that plan. Then the search begins. It may take days or years to find the rig that works for you and at a reasonable price in a location you can deal with.
We're a perfect example of this. We knew we wanted a Safari Sahara in good shape for around $25k and in the northeast. The search took six months and we ended up getting very lucky. Our Sahara literally hit Craigs List the week before our last camping trip of the season, and the seller was 10 minutes from the CG we were staying at.