Change a shower to tub? Master bath only has shower.?

Hi, what would be involved in converting a shower into a shower/bath. My master bath only has a shower, but for resale purposes, I would think it would sell better with a whirlpool bath as well. I don't have room to have a separate bathtub. Can the existing drain and lines be used? Would the floor need some type of reinforcement? Any help idea on cost, ect appreciated.