Let's look at this way what do you want of a trailer.
you could have a standy or you could have one that pop's up.
Restroom do you want to just go some where and flush or have it on board and deal with the smell and dump it.
Do you want in inside kitchen or one out back.
do you want a hard top or a tent top
a bigger one means using more gas, having more room.
fixing up an old trailer it brought up to it's original condition is a lot of work but the rewards of what others see and ask about can make it all be worth it.
you could build one like this with inside kitchen and bed.
http://www.youtube.com/watch?v=8xt8TLi_BHA
I do not know what trailers you have and are old but fixing them up if done right can make your whole world blossom in many ways.
I do not know you skills, your dreams , your love for the out of doors, nor do I know where you love to camp but it is time to start a list and see what comes out of it.
Ron