Hi JJD, Welcome to Fishlore
actually u can't estimate how much it is going to cost u, like your heater may not work sometimes; u have to replce it; some of your costly fish may die unfortunately, sometimes filters don't work; so it is really hard to tell, and money is not everything that u have to worry about, keeping a huge tank is a lot of hard work and committment, u have to spend a lot of time on it, but my suggestion is u should go for the biggest tank u can afford because they r easy to maintain.
Fishkeeping is a great hobby, i bet u will fall in love with it once u start it.