Most basements we have built had a full set of concrete stairs on one side of the basement, and then a "light well" with a crawl ladder on the other side.
I am not sure about the tax implications though.
Let me know if you need any more info from a General Contractors point of view.
If my memory serves me correctly, from a property tax perspective, basements are not considered living space; however, the city may require certain features if they are designed as living space.
If you are looking for a highly skilled basement contractor to speak with concerning your proposed project shoot me an email offline. He specializes in building basements under existing homes and does new basement construction as well (I personally helped him build a 3,000sf basement in Woodside)