This is correct. The mixture is almost always propylene glycol, vegetable glycerin, nicotine, and flavoring. I don't know of any negative effects of propylene glycol and vegetable glycerin, and as long as you don't use a carcinogenic flavoring (they exist) your biggest problem will likely be nicotine.

I don't think nicotine is good for you, but vaporized nicotine seems much less dangerous than smoking a cigarette.