Obviously, maintaining a castle in the real world is expensive and time-consuming. However, in a magical kingdom where you can simply summon a team of very hygienic and agreeable rodents to clean it and a seemingly limitless supply of guards to secure it, living in such a massive house becomes an entirely feasible proposition.
Choosing what type of castle you want is very important, as not all castles are created equal. They have to be suited to the topography, the climate and your lifestyle.
Your castle should reflect your personality, project power and be secure against invaders. If you're planning to torture anyone, it'll need a dungeon; if you anticipate a lot of war, it needs thick walls and turrets; and if you like to read a lot, it will need a totally bad-ass library. If the climate is very hot, then thick stone walls can keep the interior cool and pleasant, while if you live somewhere grey and rainy, large windows will save you a fortune in candle wax (which is just plain tactful, should your husband happen to have a candlestick for a valet). If you like a good view, then you'll want tall towers.
Just like a Disney princess selecting her own castle (and the prince inside it), it's all about your preferences and how you plan to put that castle of yours to use. Let's find out, and we'll see which princess you match with the best!