If you really want to do this, you need to engage a professional tax person to give you advice and who will defend you at audit.
In addition to the usual rules that business expenses must be "ordinary" and "necessary" for the type of business, expenses that are also in the character of personal expenses are only deductible business expenses if they would not have occurred but for the business.
You might argue that the pool is not personal and you never would have installed it but for the business, but that's not very believable. You might argue that you installed top of the line accessories to show them off, and that but for the business, you would have used standard accessories, therefore the extra cost of the items is a business expense. That might get more traction if audited.
Then you also have a depreciation problem. If you build a storage barn on your land that is 100% used for a business (car repair, woodworking, storing supplies for some other business, etc.) then it can be a legitimate business expense but you usually have to depreciate it instead of deducting it as an expense. And that affects the taxability of the eventual sale of your home, even if you would normally qualify for the capital gains exclusion.
So see a pro if you want to do this.
