a couple thoughts -
1 - have you ever cooked on a stick burner for any length of time? It about killed me. Getting up all hours of the morning, splitting and lugging firewood, tending that fire every 45 minutes - I was dead by the time the meat was ready. I know Texans are picky, but are you physically able to do this week after week? I was not.
2 - I am a business man - which is why I question my BBQ bug, but that's another topic - you got the bug, you need to do it. In any business, starting out small is the key. Unless you have unlimited capital and can go out and buy whatever you want and need, I would start out small - and used - and advance from there. If you do have unlimited capital, then I assume you are a smart businessman - and know that small bites and chewing is better than choking.
3 - the Health Dept will tell you sinks and water heater, etc - but and this is a direct quote from Mike Mills, "I don't know a Health Dept anywhere in this country who will not approve 3 = 5 gal buckets". Ask - that right there will save you many thousands to see if you like this, can make money and can do it for years.
4 - Food trailer and trucks are a cool thing - just make sure the people come. As more trucks come on scene, it waters down the dollars that are spent that evening, weekend, etc. We know. Big festivals seem to be a hit when you get in to the right festival. you can bring in many tens of thousands of dollars over the course of a weekend or two weekends (9 or 10 day deals). My buddy Jack does a Music Fest in PA - 90-100k over two weekends. Now the markup on BBQ isn't anywhere near as good as ice cream or hot dogs or butterfly fries or funnel cakes, but we don't love those, do we?
Follow your dream, just remember - a little rain is good, but a Tsunami will drown you. Slow and small, then get bigger as you need to. You may not look the coolest, but it is the right business move for sustainability.
Hope this helps.