Average Salary: $55,240
Expected Lifetime Earnings: $2,306,000
Dietitians make in the neighborhood of $55,000 per year (source). If you get an entry-level position at a hospital, medical clinic, or company, you'll likely earn much less—somewhere between $35,000 and $40,000 (source). Those who have years of experience could make as much as $70,000 per year (source).
Where you live also makes a difference; those who live in metropolitan areas have higher salaries to make up for the high cost of living.
For those looking to work independently, be aware that it takes roughly three months to go through the insurance credentialing process. Before you strike out on your own, be sure that you wait a couple of months before quitting your day job.
You'll also have to eat the cost (hopefully it's low-cal) if your patient decides not to show up. Basically, no-shows take up time that could have gone to another paying patient. You'll also have to pay for everything that goes with having an office, such as rent, lights, and utility bills.
Any marketing you want to do, like getting a website hosted or sending out newsletters to promote your company, will be up to you. There are plenty of dietitians who enjoy setting their own hours, putting out carrot sticks in the waiting room, and running their office according to their own rules.