I lived in Paris for two months and a half in summer and it was a great experience. I lived with three of my friends on the eighth floor without a lift (151 stairs) in a small studio in 16th arrondissement but we enjoyed it very much. Well Paris is actually quite expensive but i don't suppose more than e.g. London. Public transport is cheaper in comparison, museum enties are often free. Everyday meals didn't cost much provide you buy cheapest food. Just as in the UK you can choose in a supermarket between cheap and expensive food. In fact, Paris is very safe a place, you can walk alone late at night and be sure nothing's gonna happen. Of course, depending on some amount of luck, but overally life in Paris is OK.