I am about to insulate, dry wall, and place a floor in my 60 year old house attic. Since the attic is unbearably hot in the summer, I want some form of ventillation. Contractor has recommended ridge vent with roof mounted solar fan. Don't I need soffit vent for intake? Will this work with the above?

You definitely need an intake. You cannot get the air out through the roof or ridge vents unless there is fresh air to replace or push it out. With good soffit vents, you may not need an extra fan.