What's a decent estimate to add a bathroom to a rental?

[Steve S.]

I have a rental that is a 3 bedroom / 1 bathroom in a college town.  I can add a modest bathroom (nothing fancy, but functional and respectable) with a shower off the back of the house to bring it to a 3/2.

I think that would help attract more tenants and raise rents.  General thoughts on what I would expect to pay to get this done?