Alot would depend on how often you will use the steamer. There noncommercial and commercial grades out there. I have been using nothing but vapor systems now for three years. I own four machines with three different manufacturers, with my most recent purchase 3 weeks ago. If you are a full time detailer you will want one that lasts, easy to use and flexibile. Of the ones I own I recommend the Euro Steam 2100(eurosteam.com) or VaporClean TR6(kleencarauto.com). I will be purchasing the Desiderio(kleencarauto.com) in the near future. The price ranges of these systems are $600-1500 but worth every penny. I was spending ~$250/wk on chemicals prior to purchase. Nevermind the fact that the vapor steam disinfects, is a timesaver,versatile and healthier for yourself to use(no longer ingesting fumes). You will want a machine that has adjustable pressure with multiple attachments. Make sure you purchase a unit from someone that can service the machine if necessary, that is the mistake I made with the first one.
In owning these machines you also get the WOW factor from your customers.