eBay Vendors

I am considering signing up for dropship company but I am uncertain about this business model. I have a few questions that could be helpful for my research:

1. What is the average profit margin for this business?

2. I know several people making mistakes by using a business that: (a) ship items late, (b) ship wrong items, (c) item out of stock, (c) pricing too high… How to avoid those dropship companies?

3. Is there any good example of a successful company selling products by using dropship services from other warehouses? I know competition is fierce in eBay.com so I wonder if anyone making any money

4. Where is a good source for research more? bad and good of this business model?

5. I looked on Alibaba.com and their prices are often very high. Is this a good place to start?

Thanks and let me know if I need to clarify something else. I am totally a beginner and I am trying to do homework now!
I am interested to know good sources of information (including books in store). Please avoid posting another website with scams about dropship business since I have found enough of them on Google.

i know of a website that compares some of the dropshipping company, if that will help you.