If you have a shop and like your current espresso machine get one similar to that so that you can use the same repair people/parts/etc. Your mobile unit will need a generator/power source so make sure that is big enough to power the espresso machine and everything else that you are going to be running. (I run a 12K generator and could still use more power at times) A decent 2 head group should be able to keep up with the volume that you will need in a mobile unity. There probably won't be enough space for a 3 group or the people that could maximize that size of machine. Your water will be supplied from the fresh water tank and make sure that it runs through a good filter before going into the espresso machine as you might not always have the same water source.
Good luck.
