Do you mean you conduct business at your customer's location, so you don't have a storefront / office area that the public uses?
This will depend on the requirements of your government county, so call them and ask. Most itmes they want you to buy a license so they get the money, that's all. If you get caught operating without a license, you'll probably have to pay a fine that is a lot more than buying the license in the first place, so don't make a mistake by trying to save money. That mindset will cause you all kinds of problems in every area of your business and cause you too much pain. Work is so much easier when you have the right kind of tool and a high quality tool. Try it yourself, see how much pain you get when you try to cut corners. It's not worth it.