Convert basement into apartment - good idea?

[Aspen Jay]

What are your thoughts on converting a split level's bottom floor into a separate apartment? The upper dwelling would have three bedrooms and two bathrooms. The bottom area is big enough to have one bedroom, a kitchen/family room, and it already has a bathroom. I would want to close off the stairs from the main level to the bottom floor which could make it an interesting sell down the road. Any thoughts? This is a potential property that I am considering. The added income is not needed to make the numbers work, but I was just thinking of ways to get more out of the property.