I bought a site for a $1 and spent $15 for three articles. It's now making $5-10 a month. All I need is 999 more sites and I'll be making $150 a day
However, it's an important consideration on how many sites that you can "run". You may have yourself spread to thin to reach your revenue goal. Concentrate on the top 5 sites and try to add one link per day for each of the 5.