I think an enormous percentage of people in their early and mid 20s are largely clueless about predatory business practices and how they can be impacted by them. Everyone is different, but I personally may have been more vulnerable to shady business people when I was 21 than when I was 18; I was still clueless but felt more like an adult and was less likely to seek the wisdom of my parents for certain decisions. Each case is unique, but I don not think this situation is similar to an age of consent for the consumption of alcohol, tobacco, etc.