According to my point of view (yeah yeah), it is very much possible to have that many sites or even more if you take the right approach.
If you do your keyword research wisely and make your sites smartly, each site can make you $20 a day on average which nets up to $12000/mo in revenue. Now spend some of that money on outsourcing the creation of new sites in your arsenal and maintenance of the current ones and grow, diversify, grow, diversify... $$$$$$.
That is just the basic concept. There are many variables involved and many ways to go about having that many sites and still being able to enjoy your life.