No one legally.
Criminally, no. An adult, whether they're living with their parents or not, is fully responsible for them self. The eighteen-year-old, and he alone, can and will be held responsible for their own actions. In civil matters, it may depend on the circumstance. If the parent co-signed on any kind of loan or payment for the eighteen-year-old, and the eighteen-year-old does not keep up with the payments, the cosigner can be held responsible for those payments.
No! how is it wrong to like a eighteen year-old??
no.
1990
Yes, at 18 years old she is legally considered an adult and can make her own decisions for which she is then responsible for.
with your parents consent yes
Up to parents
No
Yes, both are adults.
Yes
No, when one marries under the age of eighteen one becomes an emancipated minor. In the USA, at least.
Seventeen is not the same as eighteen. Until you are an adult, the Nevada law says the parents are responsible for the minor.