For the vast majority it's a hard life. From my experience, not world vision bad for the vast majority but without a doubt access to clean water is not available to much of the population. A lot of people eak out a living doing illegal (and in most cases unsustainable) activities (turning trees into charcoal, buying one paper from a box taking them all and selling them to drivers, etc).
A decade ago a salary of $20 a month puts you near the top of blue collar kenyans. Many were surviving on a few dollars a month.
Sanitation in the slums was poop into a plastic bag and then spin it over your head and let it fly to get it away from your shack. Your neighbour a few alleys over does the same thing and it averages out with *&^*&^ spread everywhere. The water source was a few trickling brown streams (probably not much different volume than a garden hose) filled with garbage. That supplied ~100,000 people. 5 to 10 people living in each 100 sq ft shack. Fires burning in shack for cooking. Almost everything you look at isn't conducive to a long life.
This pic is reasonably representative of what I saw when I was there. For obvious reasons, busting out a big camera and taking pictures would have been a dumb idea. That water was used for cooking, drinking, clothes washing and bathing. I still don't understand how their clothes looked so damned clean.