Does this make sense-buying a used motorhome for 1 year use

It's probably even possible to find one that won't cost you that much. Depends on how motivated the seller is to get rid of it. Buy low and sell high!

Here's another thought based on your plan. Do you own a big pickup or have a need for a big pickup? You would likely lose a lot less money by buying and then selling a used trailer. And if you had a need for the truck you could buy and just keep it.