I suggest you contact an agent using the tab at the top of the page and ask them your question.
Before doing so, jot down some relevant information: the size of the house, the size of the basement, and whether or not the basement is "finished."
Do you understand a half-bath is only a sink and toilet?? I'm asking because some people think it means the bathroom doesn't have a tub. If it were me and I were you, I'd price a 3/4 bath to add a shower, especially if the basement will be live-able square footage.