I just had a situation like this at the last house we bought. Previous owner left a sail boat in the backyard, last registered in the 80's. My trouble was that the previous owner was deceased so there was no way for me to contact him. I ended up selling the boat for parts on Craigslist which got me around having to go through the state to get it retitled in my name. I don't know what the process is with titling a trailer in GA when it's found on property but here in VA/MD I would have had to ...
-Make documented attempts to contact original owner
-Put a notice in a public forum (newspaper) giving him 30 days to claim it
-Go through titling process and pay to have everything switched over (another 30 day process)
-Repeat process for boat trailer
For me, the process outweighed the reward of selling it as a whole unit. It would have only been worth about 3k if I'd sold it in one piece. I'm in the business of flipping houses, not boats so I just got it gone.
If you can't contact the original owner, you might try to list the trailer "as-is for parts" to get around the titling headache. Good luck man!