Looking for a Used (new to me) Fifth Wheel

good luck, the propane fridges are still out there, you just have to look or compensate by adding more solar and batteries.  I think most 5 wheels only include 1 battery, the second is a throw in or a upsell from the rv dealership and they are junk batteries at that, that's not to say you have to accept those batteries from the dealership.  lithium batteries are being made by manufactures in the new Mini format, so 300Ah the size of a regular battery and the price is cheaper than comparable AGM (so generally to make agm last you need twice as many AH of agm to compare to LiFePO4.  so you could easily put two 300AH mini LiFePO4 in to it and have the equivalent of 10 to 12 AGM 6V batteries (depending on actual AH) but a lot cheaper.   so LiFePO4 batteries have offset the newer electric trend to an extent.  then you could put a good solar setup and be set.  if you can do the solar your self, all the better as a 450 watt panel is available for about 200 to 250.00 right now, so for 1000 bucks you could do a 1200+ watt solar set up an as long as you don't need to run an AC, you should be golden.  well you would need an inverter also, so say another 500.  so for less than 2500 bucks you could be set up.  the dealers sell LiFePO4 batteries, but 90% of what they offer is the dragon fly brand which is the OEM name for Battle born and they are more expensive than anything else out there.  up here they want 2700.00 bucks for there big 270AH one, where I can get a LiFePO4 mini 300AH right now for about 500-700.00 off amazon.  

as for the brand, there are lots of good brands you just have to go and physically look, look at the fit and finish, look at the cabinet and drawer construction and stuff like that, junk will be apparent when you have been looking at a bunch of different brands.  mechanically they are all the same, its the lipstick they put on the structure that is different in all reality.  most use the same converters, fridges, ovens, etc.  then after a bit you will see what the cost is vs the quality of what you want, or are willing to settle for.