Assuming you would like an all-inclusive answer:
To start a mobile detailing business, you will need a vehicle large enough to transport your equipment, supplies, and materials. Many detailers use a van, SUV, or truck. You will also need a water source, electricity, and a generator if you will be working remotely.
In terms of equipment, you will need a pressure washer, water tank, hoses, extension cords, a power washer, pressure washer detergent, buckets, sponges, wash mitts, chamois, waxes, polishes, and a buffer. You will also need a shop vac, power drill, and miscellaneous hand tools.
In terms of supplies, you will need paper towels, rags, microfiber towels, glass cleaner, all-purpose cleaner, upholstery cleaner, vinyl cleaner, and tire shine.
In terms of materials, you will need tarps, drop cloths, and plastic sheeting.
This is just a basic overview of what you will need to get started in the mobile detailing business. For a more detailed and comprehensive list, please consult a professional.