Documents for parents' B2 Visa

Hi, I need help on what documents I need to send to my parents for them to apply for B2 visa in Shanghai. I am a US citizen and it's the first time for me to invite them to come to visit me.

I heard about Affadivit of Support (I-134), bank statements, etc. since I just bought a house, I have only a few thousand in the bank as deposit. Is this going to be a problem?

Can someone please provide me a list of documents I need to send to my parents? When I asked the Visa information center in China, I was told all I need is a letter to invite them. Is this true?

Thanks in advance for any information you may have.