In France, anybody may get established as a translator, regardless of his or her diploma / qualification. Your friend possibly thought about this aspect? Translators have no "Ordre de XY", unlike doctors, lawyers, dentists etc.
But certainly, they must be registered with URSSAF etc. for tax and social matters. This is quite a different aspect.
I suggest that your friend may ask again, why not on Proz and in French, in order to clarify the question. But please, start by having a look at older discussion subject. The question is not a new one and anybody who is fit for becoming a selfemployed translator should be able to get that kind of info straight by himself (imho).
OK, thanks for helping out. I really just wanted a yes or no answer, as I've always worked in Spain and there are no similar requisites AFAIK.