Land almost always goes up in value so I think it's probably just a convenient place for him to stash money if you don't have to pay taxes on it.
Do you get taxed for owning land like this if there's no property on it?
If you own the land and there is no property or any farm-related use to it, you still pay property taxes at the highest rate possible per the IRS. Because you aren't generating income on it, you don't pay income taxes on the federal, state or city level.
Now, if you own the land and it has farm-related equipment and farm-use to it, you do pay taxes, but you usually pay much less and there are many incentives to owning farmland.
While income from normal farm business is taxed at the Federal level, it's much lower than standard federal taxes given that your land is assumed to be used for the betterment of society. Also, many states offer tax benefits for farmland owners, particularly in the form exemptions from sales, use or property taxes. Additionally, property taxes paid on farmland are tax deductible. You can also write off items purchased for use on the farm.
So, Bill Gates won't be hurting due to excessively high taxes on the land, as he'll likely keep most of it under the guise of farm-land. Owning land is a wonderful hedge against inflation and a bad economy.
Like that old saying, when in doubt about what to invest in, buy land, because God isn't creating any more of it, but he's sure creating more humans in need of land to live on.
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