Well, I always read people would buy warm meals in the thermopolia (shops) in the streets before coming home to dinner. Most of the insulae structure was made of wood - specially the floors and beams - and would easily burn. Perhaps that's also why the poor that lived in them wouldn't have lamps. According to my research, they didn't have money to pay for oil to feed the lamps, and perhaps they just didn't need that anyway: poor people would start working with sunrise and surely wouldn't want to go on working when it got dark.

Water supply was available in the inner court, where people would usually have a fountain fed by public water supply coming from aquaeducts, when necessary. There were no toilets inside the apartments, and so people would discharge their urine and feces vases in a main vase in the stairs, the "dolium". Other sources say people would simply throw the filth on the streets below through the window...!

Well, life in the insulae seems to be s lot more fun than in the wealthy domus!