1.) if you are professional always do a contract
2.) being professional means that you have to pay taxes - taxes are costly (and so you can take away around 35-50% of the hourly wages to get to a real rate) - most probably you also have to come up for your health insurance which also can get expensive (in some countries the company pays it, if you are employed)
Regarding to copyright talk with an lawyer specialized into that topic and he will tell you all the little details.
Since game art is mostly project based, the freelance rates compared to other graphical jobs are lower, however, since jobs can go on easily for hundreds of hours, the risk is smaller than like for web design (where 150-200$/h is a common rate, but yeah, there you don't know when you will get the next job and the briefings are usually more complicated as well).
THe country where you live also plays a big role.executive field:
0-10$/h working for free, first gig, deviantart offers (unprofessional field)
10-15$/h beginners, students (unprofessional field)
15-30$/h young, talented artists
30-40$/h established experienced artists
40-50$/h world's top class
there aren't really established flatrate values, those always depend.why is it like that?
-quality/time (experienced artists produce better quality much faster than beginners, beginners will most likely need much more time and the result will be much worse in terms of quality than what an experienced artists produces in the matter of minutes)
-experienced artists will have established workflows and can completely switch between style directions, because they are perfectly able to control what they make - this leads to less revisions
Means in most cases it really pays off in the long run to hire an experienced artist, who knows exactly what he is doing.design agencies:
up to 200$/hart direction/art asset planning
40-120$/h (huge responsibility, one wrong decision in the art design process can lead to multiple thousand of dollars budget changes for a whole game project)art scene/popular artists:
200$/h and higherG.A.G. Guidehttp://forums.tigsource.com/index.php?topic=36539.msg963792#msg963792Old article on gamasutra:http://www.gamasutra.com/blogs/AdamSaltsman/20090724/2571/Pixel_Art_Freelance_Best_Practices__Guidelines.phpGame Budgets:http://blog.mostlytigerproof.com/2010/09/18/game-budgets-a-powers-of-10-overview/Art direction rates USAhttp://www.bls.gov/oes/current/oes271011.htm
Freelancing means that you have to do all your stuff on your own, all your bookkeeping, all your mails, all your working times etc. You are self employed, your own boss and you are fully responsible for what you are doing. Nobody will pay you for answering initial e-mails.
If you want to freelance professionally:
first compare your work made by other professionals
a) how much do you need to make a living (with all costs included)
b) how much hours do you want to work
calculate hourly rate (and look if you are in your range)
do you get enough jobs?
does anyone pay your hourly rate?
if yes, great
if not, maybe you aren't working enough hours, your quality is to low compared to your concurrence, you lack something, you are working to slow...