For any type of business to succeed, you have to get paid. So whether you do one freelance gig a month or run a full-time writing business, you need to calculate the time you've worked and bill your clients for it.
Sales Tax: Depending on your jurisdiction and type of business, the tax requirement can get complicated. Be sure to follow instructions from your local tax bureau and include the appropriate tax amount on the invoice. Pro tip: Use an invoicing software to manage your business activities, change tax settings as you want and make your tax time easier.