I own an undeveloped city lot. If I sell it, how am I taxed?

It depends on whether you’re viewed under the tax law as a developer. If you hold the lot as investment property, any gain you reap is taxed as capital gain. You may also owe an additional 3.8% tax on net investment income related to this gain. But if you’re a developer and your lots are essentially part of inventory, your gain is taxed as ordinary income. And because you are in business, you won’t pay the 3.8% tax as long as you materially participate in the business’s activities.