Professional blogging is a full time career, there is no doubt about it. All the professional bloggers in the world are full time bloggers and blogging is their full time business and job.
The owner of labnol.org is a Professional Blogger. The owner of shoutmeloud.com is a professional blogger. Similarly, the owner of copyblogger.com is a professional blogger. There are many such professional bloggers in the world, who give their full time in this career.