Re craigslist trailer - I do think that it is on the low side for the 16 hander. A 7 ft tall trailer would do you much better (6'6" used to be the average size back in the 80's (my first trailer that I still have but don't use is 6'6"); now 7' is the new norm). Also, I'm not keen on a solid divider as I think it does not let a horse spread its feet out more if it needs to balance itself. Now if you were just going to haul your 15 hander and removed the divider to let him stand the way he wanted, that trailer just might do. You could get it for the interim, use it for awhile and give yourself an idea of what your needs really are, then sell it on and buy another. If you decide to purchase get a mechanic sort of person (if you're not) to give it a good check out looking in particular at the condition of frame, floor boards, wiring and breaks; also take it for a test tow if you can to see how it pulls.
Re finding trailers - Many times this can be futile as there never seems to be that many good used ones and they get snapped up right away. That is why I ended up buying my second trailer new. You can check out dealerships in your area as they may have taken in one on trade. However, don't expect too much here as it seems for the two/three horse models, most people either keep their old trailers or sell them privately. Other places to look are farm papers in your area, internet sites such equine now.com.
Re other options - you might want to consider a stock trailer. They have smaller tagalongs/bumper pulls that can carry two or three horses easily. Those are about 14' long. The only thing you have to watch out for is the height as a lot of the older ones are only 6'3"; on the plus side it appears that most of the new models are now 6'6". Since stock trailers are very open, horses don't seem to mind the lower ceiling as much. Generally, if all things are in the same relative condition, you would pay more for a horse trailer than a stock trailer of the same age. I've seen brand new stock trailers in the 12' or 14' length advertised for around $5,000 where I am.
Please remember to post pictures when you get your trailer -- Good luck with the hunt and you'll love having one.
Last edited by Chevaux; 06-24-2013 at 06:40 PM.