This varies greatly and many people don't even attempt to make money off their blogs, at least not directly. One of the reasons is that people are more interested in sharing their information and developing a good community than making money. Another is that many blogs won't generate enough traffic or write the type of posts that will convert their traffic into revenue.
Earlier this month, Darren Rowse of problogger.com put up a poll asking visitors how much money they earned blogging in the month of October. At the time of this writing, there were nearly 5,000 respondents.
Darren runs a popular blog about blogging for money and makes a six figure income from blogging according to his posts. His problogging site gets hundreds of thousands of visitors a month trying to emulate him. Based on his blog's content, it's likely that the majority of his visitors have an interest in making money blogging. So let's see how they do.
The largest portion of respondents 35% didn't make any money blogging in October. That may be because they don't actively put advertising or affiliate links on their sites, but as I said, the site is about blogging for money so you would think many that didn't make money blogging are trying to.
The next big group (18%) are ones that made less than $10 in October through their blogs. But with most online advertising programs have a minimum you need to reach before you get a payout. For example, a popular program from Google Adsense pays you when you reach $100. Until you reach $100 dollars, your money just sits in escrow. So if you're making $10 a month through AdSense, you'll only receive a check or electronic transfer once a year.
Since many bloggers use AdSense, lets look at how many people don't earn enough to receive a monthly pay day from Google. This isn't exact since not everyone indicates they make money through adsense, but $100 a month is not an unreasonable expectation people have. It is also important to receive a regular payment. Not everyone uses free blogging sites. Many people have hosting costs and other expenses to worry about. It's nice if your blogging can at least cover your costs but if you're expenses are monthly and your earnings are annually, it may not seem worth it. Of those that made money in the poll, 34% made less than $100 in October.
For the 11% of bloggers making $100-499 a month, it's not enough to live on but it could help pay for a nice vacation each year, provide extra money to savings or if you'd rather spend it, it might make you consider a BMW instead of a Toyota.
If you're a single person in the US making less than $10,400 a year, you're below the poverty line. That's less than $900 a month but to work with the data Darren provided, let's say you need to make $1,000 a month to live out of poverty if blogging is your only source of income. That could mean that 50% of bloggers who make money would live in poverty if their only job was blogging.
If you want to be a problogger like Darren and make a six figure income from blogging, the odds seem to be against you. Only about 6% of participants in the poll make enough from blogging to claim an annual income over $100,000.
Keep these numbers in mind, especially when considering to buy products and services that claim to help you make money online.