Warning...this is going to sound very discouraging :(
I run a successful ecommerce site and work with over 400 blogs. It is extremely difficult to make a profit off a blog. It didn't used to be that way but the market is pretty saturated at this point and businesses such as mine have to raise our standards significantly on whom we will pay for advertising. Advertising is a very difficult way to make money. The bloggers I know for sure are making a profit (and I can count them on one hand) are primarily making their money off selling content (ebooks, online classes, etc.) but even that is very hard to do.
I have two ways of working with blogs. The vast majority are through an affiliate program where the bloggers get paid a percentage of the sales they bring in. Only a handful of bloggers end up making more than $100 a month (although a couple do fairly well). I have a very short list of blogs I pay for advertising and they have to be blogs (or blog networks) with very high traffic numbers--numbers that take years to achieve if that even happens. I cannot tell you how many new blogs e-mail me each month wanting to sell advertising. While I feel their pain, the best I can do is let them sign up to be an affiliate.
As a side note, blogs are a lot of work. I know bloggers who work well in excess of 40 hours a week and still don't turn a profit (and I should say there isn't anything "wrong" with their blogs, some have high traffic numbers, and have been doing it for years). It's just the nature of the market.
Blogging is extremely easy to get into and there are enough stories floating around of bloggers making a good living to incentivize people to jump in. In reality though success is extremely rare and since anyone can get in, everyone is. It's very hard to differentiate yourself in a manner that will attract high levels of traffic and consequently companies willing to pay for advertising.
Having said all that, blogging can be useful. For example, it can be a great way to connect with your customers on a regular basis, to humanize your company, etc. When that is the goal, blogs can be very successful. I just wouldn't encourage anyone I care about to start a blog with the goal of making money.
Follow Mothering