#1. Before you start anything check with your local Planning & Zoning Office. See if what you want to do is even possible. They will TELL you how big/tall you can go. There will be setbacks from property lines to consider. They will require engineered plans to be filed and you will pay for a building permit. No sense in building something and then Big Brother telling you to tear it down. Don't try to sneek it in, your neighbors will rat you out.
#2. Bigger is always better.

Yes, I have done the preliminary checking on zoning etc. Not sure about height yet. Once I have chosen size and features, I will hire a contractor to supervise things. It will be money well spent. Land needs preparation, tree needs to come down, cement poured, more than I can handle since I've never done any of this before.