what are the steps to starting a cosmetics line?

[Jake]

Brand image and publicity are a huge part of that sort of business, I would image some spend more on advertising than actual product production. Reselling established brand names would be a much shorter term business development.

One huge shortcut, try a web search for White Label Cosmetics, provided by manufacturers who put your own brand label on generic formulations, a fancy label design might cost nearly as much as the product in some cases, it's important that any ingredients listed accurately reflect the manufacturer's data.

There are sites with tools that help you come up with fictitious names, including: wordlab.com, naming.net, wordoid.com, lingzini.com, namestation.com, some of these tools look up the domain name availability as you go.
Any name not already used in a .com web site name is probably not trademarked.