For sprinkler repair and replacement of solenoids you don't need much specialty equipment. A shovel and a continuity tester is the most important. A wire tracer would be nice but I don't have one.
I do almost $100,000 of sprinkler repair and all I have is shovel, continuity test, PVC pipe cutter, and glue. I use a cargo van to carry supplies. Going to the store for parts will kill you. You can't charge for the time you are at the store and travel time to the store and back. A van was the best thing I bought.