If you want to find a JM model, I would suggest following Gunbroker for a while. I found one that way and am quite happy with it. Yes, you may not find a great deal, but chances are that you can find one in good condition on Gunbroker.
And even if you do not find one there, it will give you an idea of what they are going for in case you come across one used. I have heard of guys finding great deals in pawn shops, gun shows, etc, but I do not see Marlins come up used very often where I live.
FWIW, I now have three JM Marlins that I have acquired that way, and all are good shooters. All are also in good condition despite the age, so I am happy.
Good luck on the search.