From what I know, a realistic scenario is..
Find a studio and apprentice while you're learning, if you make more than $5,000 the first year I'd be amazed, BUT, if you get involved with logic, pro tools, or live, then you will more than likely be involved in the songwriting and arranging. Then your income has a greater potential. In most of the studios I work in, the artist writes a song, the engineer/producer makes suggestions (usually to get a piece of the songwriting credit), and winds up getting royalties if anything happens.
I've done sessions where when I leave the studio, I ask the producer who wrote the song, three months later when I hear what's going to be released there are up to 6 people on the list compared to the original one.
Get involved in the songwriting and it'll help, although there's nothing predictable about this business...
