Statistics on freelance developers are hard to come by as it’s not guaranteed they are reporting accurate numbers and not often do freelance developers report their income to third party sites.
According to ZipRecruiter, the highest freelance salary reported to them is as high as $128,500 and the lowest is $24,000. They believe that the majority of salaries are between $53,000 to $84,000.
Due to being freelance there are not many opportunities for increased pay or job advancement as people work for themselves or in a small team.
Benefits of being a freelance designer is that you get to work on what you want and choose which jobs you want to take. You would also work remote most of the time and could work however often you feel like.
