Just my two cents....
You said that you are interested in catering but don't have the right equipment, ie not enough room. One option, buy a bullet smoker, WSM, or other such smoker and find that there is not enough room to do anything in volume. Sure, you can buy several of these units, and cook that way. The other option is to look into stick burners like Mike said. The bullet smokers are great, that is if you like charcoal...., but for doing any kind of volume...., they are lacking. You have to remember a lot of the people on this site use there cookers to compete in competitions. I personally use my cooker, I have a Lang 84 Deluxe, to feed myself and a LOT of people, ie catering. Now, these stick burners do require the use of more of your time because you have to tend to the fire a little more. As far as the results.... I feel the use of real wood, and not compressed petroleam by products, is what the essence of what BBQ is. Now as far as cost is concerned, my BBQ was about 5000$ after shipping to my door. That may seem like a lot, but when you consider that I can easily feed 150 people, or cook for my wife and kid, I know I made the right choice.
If you are truly hooked on doing the BBQ thing, you may want to look into the stick burner route. I don't know any of us that made the investment that are on this site complaining about having too much room on there smoker to do whatever they want. Now the guys here that have Bullet smokers couldn't even think about doing an entire hog. In fact, my smoker can do about 300 pounds of meat at a time, and there has been times when I wish I had a bigger one.
Now is this investment more than 150$?? Certainly. Is it worth it?? Wouldn't trade mine for the world...............