Melissa Shelton is a has a pyramid sales for the oils and states on her own website that >>"refuse to work with anybody who won't use YLEO" ... which is financially her baby. By all means do research, but look for people who are not doing their own quasi research with no peer reviews or adequate oversite, with a goal to sell their product.
As for Young Living Oils... wow: https://www.linkedin.com/pulse/20140713001220-36302273-the-truth-about-gary-young-young-living-essential-oils