It is not easy to manage even a single blog. Having 100 blogs and managing it with unique contents required full time, dedicated person to run it. Most of the bloggers will give up writing at some point of time. Having one blog will only make you look bad in one domain. Having multiple blogs, especially those with hundreds of blogs will face even bigger troubles. In average, most active bloggers will write one blog post in every 3 days or 2 blog post in every week. That leaves us with an average of 10 blog post a month for a blog. Writing an average of 200-250 words post is a common length for a blog post. Having this average numbers give us concrete numbers of post for us to work on multiple blogs.
If you want to run 100 blogs, you need to write at least 1,000 posts a month to keep all 100 blogs look active in search engine, viewers, bots, etc eyes. Writing 1,000 posts, each 200-250 words within 20 days; counting four working days in a week, to support one month blogging. You need to write 50 blog posts each day consistenly for 20 days a month to support all 100 blogs. If you can write a blog post within 10 minutes, then you need at least 8-9 hours a day to complete all 50 articles for your blogs. Leaving one working day to do posting on all 100 blogs in a week completes your five day a week work schedule. Now, you can proudly call yourself as a full time blogger.
Of course, you can use auto submission tools for social bookmarking and twitter to help your backlinks. Consistently updated blogs will get good page rank from Google as long as the content is unique. Some experts even claim that blogs with consitently updated unique contents can get PR3 within first page rank update. Having 100 blogs will give better income generation from blogging but it is extremely time consuming. If you are in a position to employ people, then it will be easier. Having an established blog can earn at least $100-$200 per month considering you are active in hunting opportunities in webmaster forums. Of course, if you can make $10k-$20k a month from all your 100 blogs, you can employ some extra manpower to your organization.