When my parents moved to Florida I designed and built some trellises for their climbing/vining plants. I made them 2 feet wide and 4 feet tall (not counting the part that is planted in the ground). That size worked for Honeysuckle and a Night Blooming Jasmine. Other plants might require different sizes. If you plan to mail these it might be best for you to investigate shipping costs; also, would be customers be willing to do some assembly?
There is a Forum here on NGA where people can post items for sale:
http://garden.org/forums/view/...
Here is a trellis I designed but
forgot to include diagonal bracing
so it ended up a bit wonky once the plants began to climb.
