Actually you can get a mid-to-high line diesel in your price range if you can live with no slides or maybe even a single slide. That probably means a 96-99 model. Prices on these units are quite low. Check out rvtrader.com and see what you can get in the under $50k range.
But gas is fine too and you can get a newer rig with more slides for the money. We just traded a 2002 Dolphin LX on a Workhorse W22 chassis, a high end gas model with two slides that would now retail for around $55-$59k. That has the 8.1L GM V8 and a 5 speed Allison transmission, an excellent combination. That combination came on the market in late 2001 and is available in several makes & models, many of which would sell in your price range. A regular Dolphin or a Sea Breeze, for example, would be under $50k for an 02. So should a Winnie Adventurer, Gulfstream, etc. You can get a similar coach on a Ford chassis with the good V10 engine for less money, but it lacks the excellent Allison 5 speed. Ford added a five speed a couple years later, but those may be out of your budget range. The 5 or 6 speed transmission is a big plus for a large motorhome. The Ford V10 and GM 8.1L V8 are significant improvements over their predecessors (454 GM V8 or 460 Ford V8) and can be expected to last well over 100,000 miles without a rebuild or major repair, but the earlier engines are no slouches either.