I wish I had an answer for you. I would suggest calling an RV
dealer and asking them where you can dispose of it if you no longer
want to use it and can't sell it.
If you want to sell it as is, advertise it in the RV Trader.
Someone will buy it. My friend sold a really old and need of
repairs RV last winter for $800. The buyer is going to use it as
her art studio. You never know until you try.