The lower class Romans lived in apartment houses usually behind or above their shops. In some apartments the whole family might be jammed in one room. Lots of houses were made of wood and had fires in them so that was very dangerous. They did not have toilets so they had to use public latrines.
The upper class Romans lived in single family homes. They had toilets and some even had running water. The upper class Romans had a lot more money. Hence, the upper class had a lot more amenities. They also had alot more land than most of the lower class Romans.