A concession trailer should be a pretty familiar site if you live near a fairground or circus. They are basically food trucks, used to sell products such as ice cream, cotton candy, popcorn, funnel cakes, or any circus or fair food.
Several guides for the purchase of a used concession trailer are available online. In short, yes, there is a market! There is a helpful eBay guide entitled "How to Choose a Used Concession Trailer".
For the average 12 ft x 7ft trailer it should cost you about $4000 - $5000 dollars. After researching on the internet, that is the average price of a concession trailer.
You can purchase used concession trailer over the internet at www.concessiontrailers.com/list_your_trailer.htm. Another good website is hubpages.com/hub/Used_Concession_Trailers A great place to look for a used concession trailer is Craigslist.com. If you can't find one locally, search other areas and ask if they will deliver. There are also many used concession trailers on Ebay, some with delivery options.
You can find affordable concession trailer anywhere. Just try going to target or walmart. They may have smaller ones you can get for cheap for snacks to sell.
There are several companies that sell used concessions trailers. Some used equipment stores also sell used concession trailers. Recently I have found several used concession trailers for sale on either ebay.com or craigslist.com. These sources are likely your best bet as it is difficult to find dealers of used concession trailers online.
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A concession trailer requires inspection. To operate one a Colorado Commercial Food Trailer Health Permit is required.
Try searching on craigslist.com to find a concession trailer in your area. After you find something, then go to the person and check it out before you commit to purchasing it.
You can buy a food trailer in Texas at Festivals and Shows. This is there website: http://www.festivals-and-shows.com/used-concession-trailers.html.
You should inspect the electrical and lights of the trailer. These are both important features.
You can order a fully furbished food concession trailer at www.customconcessions.com
Used Vending has an assortment of used concession trailers one could purchase. One can search within their results to find various trailers and carts to suit ones needs. Amusement Trader has many listed for sale as well.