How much light very much depending on what you're going to do in the space. Obviously you need a lot less light if you're just going to park cars and use it for general storage than if, for example, you're setting up some kind of workshop. How do you plan on using the space?

Currently, it won't be set up as a workshop, but we want to make it able to function as one in the future. My husband's current plan is to put in 6. He would have pull cords on the two that would be covered by a raised garage door, and leave them off most of the time.

Pull chain fixtures make as much sense as any other plan. If you don't find 6 bulbs enough light, those Y adapters can be added to double the number of bulbs. When you get around using the garage for a shop, then switch out the bare bulb sockets for fluorescent fixtures and add task lighting over tools or work benches.

Thanks for your input! We'll be going forward with the 6 lights.