First, you should think long and hard about your blog subject (your "niche").
I might have the world's best blog, but if it's on a subject no one's searching for, I will get no traffic and no income. To find out what people are searching for, use the estimator tool in Google Adwords (free) or download a program like Traffic Travis 3 (free).
As well as being popular, the subject you choose should be easy to monetize, preferably with affiliate links rather than PPC ads.
You should also choose something about which you really enjoy writing. That will make it much easier to keep going during the long months when nothing seems to be happening.
It takes months to get a site ranked decently for even moderately competitive terms, so I would expect little traffic - and virtually no income - for a long time.
If you want to get enough traffic to make a dent in your income target, you'll need some well-thought-out SEO, so it's worth taking the time to read up on the subject.
Even if you do everything right, making $1500-$2000 a month on one blog while working 2 hours per day is a pretty ambitious goal. You might consider having several blogs or sites in different niches, a common strategy among affiliate marketers.