I have in the past set up a dozen or so carts on the East Coast and live and work here in Seattle now. I have access to many resources and names of cart manufacturers not advertised who do custom work for some of the larger chain hotels, etc. If you are interested in a complete package soup to nuts, we need to start with how much CAN you spend? I wont pretend that it will cost you less than $20k but if you look for easily repairable equipment bargains and of course NEW refrigeration with a warranty, the most you will spend with signage a small register and the works, will be between $15-20k depending on what you want it to look like. Beware of used carts for sale claiming to be turn key for the flat rate of $12k they always have issues.....cheap machine, not NSF or too small to meet Health Department requirements in your area, etc.
Let me know if I can help
Although BOOSTERBEAN makes some good points, don't worry about your budget at this point. Most importantly you should research your spot first. If you don't have a location first, and a good one, all is fore not. As I mentioned in my last post, visit some of the cart businesses in your area and ask questions. If one is not willing to share with you, then continue on to the next. My point being, you've come to this forum to ask questions, why not ask them in your own back yard? Most people love to talk about their successes especially when it comes to their businesses. Be honest and up front with them, also insure them that you don't plan to open up next to them. You might be surprised by their helpfulness. To tell you the truth the more work you do and learn on your own, the more valuable this information becomes. Then after you've done what you can with the information you've collected, sit down and pencil things out. It will take you at least a couple of months to get to that stage. If you are looking to get things going any faster, then seek the assistance of a qualified consultant in this industry. Not a Johnny-come-lately, but someone that has actually owned and operated their owns locations. Contact and interview a few, it never hurts. Just a couple of things for you to chew on...
Location, get a good lay as to how much space you have to work with and if it's going to be indoors or out or both. Choose your equipment and cart by shopping around, look at your options in this area, also make sure you are getting something that's not going to overdo/underdo your operation.
You are needing more then just a box on wheeles, there is equipment and supplies that add up, so $12k is a good figure to set aside to have everything you need to open shop, more or less depending upon how far you want to invest in supplies and how high end you want to go with the equipment and facility.
You need to be up to code which can be an obstical in 3 areas. 1st, you need access to a full commissary, ie. 3 compartment sink, mop sink as well as will normally be drawing minimum of 40 amps of power to run everything so may require an additional high voltage outlet. And you'll need to store it, or keep it secure at night. Other then that, it's a nice small package operation that has serious potential to generate a formidable income or more.