My income from online biz, which is my only job, keeps going up every year. However it's because I am trying hard to diversify my online income streams. I have about an equal amount of adult and mainstream sites.
I have my own retail online stores where I sell items I buy wholesale, ebay sales, Amazon sales, normal marketing sales sites, adult blogs, dating sites, tourist sites, sell ads on sites, hosting accounts, SEO guy and lots more.
I just made 2 new hentai sites that are doing well, making a new mainstream site today, got a few more in the works. Frankly I can make as much as I want online. It's only limited to the amount of time I have to put into them.
Never stick to one thing, you'll get killed every time.