Adding a new bathroom will often recoup at least 90% of your investment when you sell your house, while remodeling an existing bathroom will usually pay back around 80-90%.To start off, you may want to start an ideas folder. Put in clipping from magazines of features you may want. Then prioritize items into things you “need” and things you “want” - unless your budget is unlimited, then you only need a “want” list. Next, decide if you want to keep the existing floor plan or if you'll need to rearrange it or expand it. If the floor plan will change, create a layout of your new design on graph paper.