Unless you are way out in the middle of nowhere... then Craigslist, Thrift Stores, and perhaps second hand stores and pawn shops would be the place to look for good used MTBs and Hybrids.

Shipping is way to high to be hunting for a $100 bike on E-Bay.

Only use E-Bay if you have some very specific needs. Titanium? Classic Carbon Fiber, etc. But, you're asking for a bike for a newbie... find something simple. Try it out. Then consider alternatives for your next bike.