Yes, you can keep everything where it is currently, you import into Lightroom using the Add option. New folders can also be created on import into Lightroom, or at any time thereafter using Lightroom (not your operating system). Importing takes up very little extra space.
Let me point out that in my opinion, organizing has nothing to do with folder or file structure. NOTHING. The two can be and should be independent. The better way to organize, in my opinion, is to simply leave photos in their existing folders, then add new photos to default named folder (such as capture date), and do the real organizing in Lightroom using Lightroom tools -- keywords, captions and other metadata. Add keywords religiously to your photos, and add captions as appropriate. This gives you a much more flexible and powerful organization than anything you could achieve using files and folders, and gives you much faster and more powerful searches as well. So, please, stop worrying about folders, and start thinking about adding meaningful keywords and captions to your photos.