The basic premise of drop shipping is that you (and many others like you) are acting as a distributed sales force for manufacturers and wholesalers who either cannot or don't wish act as retailers. You will become virtual distributors for them, while they handle the physical order fulfillment and shipping, only. As such, dropshipping is lucrative for everyone involved.
Though there are countless items available for dropshipping, it's easy to get carried away with the possibilities. It's best to focus on just a few very carefully chosen items to get started.
Not only does this keep you from getting confused with all the items you have for sale or being overwhelmed with auction fees before you actually sell anything, but you'll also be able to evaluate the feasibility of each item on a small scale before you become dedicated as a well-
known seller of Norwegian Cuckoo clocks, or some such.
The same is true of choosing a drop shipping partner to work with.
Don't just pick the first one that comes along and meets all your criteria as far as their merchandise is concerned.
Shop around and find a few that will give you the best possible deal. Then, evaluate their performance before making any type of long-term commitment. It is, after all, likely that legitimate dropshipping partners will be evaluating your performance, too.
When doing business with manufacturers, it is very likely that they'll ask you some perfectly legitimate questions about your business, such as your Tax ID number.
In the US, this means you'll be doing business as a Sole Proprietorship
(until you register with your state as something else). As such, your Tax ID number is your Social Security number. Though this means you'll be personally liable in the event of trouble (unless you incorporate with the help of at least one and usually two other people), it also means that you can get right into business without filing any forms with government officials.