the bathtub sounds like a good idea. that way you'll never have to worry about drainage issues of your res. simply pull the plug and off it washes into the tub (that is, if you don't intend on recycling the solution). i take it your bathroom has an exhaust fan? the problem with those is that they are generally far too weak for a hydro grow, so you might want to consider upgrading it. and having your water supply near the grow environment can't hurt either. but you should be more specific with what you intend to grow. how many plants? whether or not you're going sog or scrog? you can also use the bathroom cabinent under the sink as a clone/veg area, with the rest of the bathroom designated for flowering. mind you i have very little experience, but just thinking about it intuitively, the bathroom sounds like an ideal growing area. i'd like to help you out but you'll have to be more specific. just think about it, almost ANY indoor environment is suitable for growing as long as you have the RIGHT EQUIPMENT. what's your budget? things to consider...later