Without any further information...I have no idea. There are a ton of factors, and you list only one. There are four people, but are there four bedrooms? How many bathrooms? How much additional living space? Are utilities included? What's the location like? What's the area housing market like?

I was renting rooms in Williamsburg, VA for $450 a month, but that included utilities, and it could have been $550 considering the location and how nice the place was. Hell, $600 might have still gotten me somebody.