I don't think it has to be convection I think it must be commercial grade. You can get conventional and convection commercial grade ovens, electric and gas... Here are a couple of places that I have saved in my favorites
http://www.bakeryequipment.com/bakery-equipment/bakeryequipment.asp
http://www.centralrestaurant.com/
HTH
it depends on the rules in your area.
i can't....but in the next county they can....so you just have to check...
i know its a big investment....but a commercial oven saves you so much time.
i saw on the food network, someone was able to get one on ebay for 500.00...lucky dog!
Check for used restaurant equipment dealers in your area too. They are usually very knowledgeable about what the requirements/laws are in your area, and most of the time they include a 30-60 day warranty on anything they sell. Of course, if they are any good at sales, they will tell you what you have to have and then try to sell you more than that, so keep your guard up! 
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