Every state has business opportunity laws that require certain disclosures for you when you buy into an opportunity. Most states also have franchise laws that make even more disclosure requirements.
Online is different and yes there are many scam-buster type websites; just open Google and type scam and you'll get an abundance of sites.
All the Best
Brad Sugars is the founder and chairman of ActionCOACH. As an entrepreneur, author and business coach, he has owned and operated more than two dozen companies including his main company, ActionCOACH, which has more than 1,000 offices in 34 countries.