ArvelAmaya,
I cannot say for sure, and I don't know any e-writers that do it strictly through e-fiction.
In truth, many fiction writers--if not the vast majority (ebook, print or otherwise) who have a decent track record/mid-list, don't earn enough to support themselves completely--or at least a family.
That said, it's not impossible. One of the interviews, Sandra Kring, I know she earns her living writing fiction. However, her publisher (Bantam/Dell) is mainly print. She does okay but she ain't living in any mansion either.
R-Tech