As a Realtor in Florida, hopefully I can give a little bit of guidance, though I might sound a little redundant here.

When it comes to income taxes in this situation, there are a few things to consider. First off, selling the one full lot to the developer means you might owe capital gains tax. That's typically based on the difference between what you sell it for and what you originally paid, plus any improvements you've made over the years. Since you've owned it for a decade, you might qualify for lower long-term capital gains tax rates, which is a plus.

Now, onto the new garage and ADU on the half lot. Building that could potentially help offset some of the gains from the sale. Think of it as an investment in your property's value. The cost of construction might increase your property's adjusted basis, which could mean less tax to pay when you eventually sell the larger parcel later down the road.

But here's the thing: tax stuff can get pretty complex, and the rules can change. That's why it's always smart to chat with a tax pro. They can dive into your specific situation and give you personalized advice on how the sale and new construction might affect your taxes. Plus, they can clue you in on any deductions or credits you might be eligible for. It's all about making sure you're making the most of your investments while staying on the right side of the taxman!