Help with buying a Mandolin for beginner?

First off can I say I am a complete novice. I would really like to start playing the mandolin. I have had limited guitar experience from high school but never even picked up a mandolin. I have always loved the sound of them though and would love to buy one. So heres my question(s). Is there anything I should look out for as a beginner. Is a roundback or a flatback better?.How much is a decent one roughly going to cost me? I don't need a super duper one.Is ebay okay to buy one from or do you reccommend going to a music store? Any help would be greatly appreciated. Thanks