One stone at a time and keep at it.
To get on the castle building list, you must have approved land or the proven ability to purchase castle land. Castle costs: Average cost for a castle tower ranges from $150,000 to $450,000. Stone cottages or lodges start at $159,000. A stone cottage with a castle tower added start at $359,000. Typical main castle keeps or cathedral halls range from $500,000 to $3,000,000. Add the number of towers, number of halls or keeps, and that will tell what it costs to build your castle. For example, a three tower castle with keep will cost anywhere from $950,000 to $4,350,000 depending on the design, site, and/or location.
All you have to do is be able to afford a castle, and then we take the rest of the task start to finish.