Merging Two Properties

[Dante]

Per chance there might be someone here who has experienced what I want to undertake, so before I seek legal counsel and pay out the wazoo for it, I'd like to pose a question here in hopes someone may have already "been there, done that."

I have an opportunity to purchase a home and property directly next door to my current residence. I've been considering building a new home in recent years, but I enjoy my present location as it is (although my house is very small).

What I would like to do is purchase the property next door and then tear down the house (which is in dire need of repair and remodeling), and also tear down my present house, and then merge both properties in to one and build a much larger home on the property.

What legal procedure do I need to go through, after the purchase of the property next door to mine, in order for for the property to be recognized as a single piece of property instead of two? How do I go about merging both properties as one so I'm not taxed for two properties?