Don't get a 20" kick for a toddler. I'd recommend the Sonor Safari which has a 16" kick drum that's perfect for kids and actually sounds nice. Look for a used one if that's your gig. Then you'll need cymbals and hardware... welcome to drums! I'd look for used stuff on Craigslist or eBay that comes with cymbals and hardware, you should be able to just search "18" kick" or "18" bass drum" in Music Instruments and find some on Craigslist.