If it doesn’t depend on the wealth of parents, it’s fair then. Not sure it’s true. In US it depends.
Barbara, prenup means marriage. Marriage is government solution. So let’s forget about it. It must be bad.
I do not think prenup cover child support. It only covers alimony, which is another issue. Alimony can be avoided by not getting married in the first place anyway.
What about commitment outside marriage?
If a woman say, she’ll have sex with you and whe will only demand $500 per month or $3k per month, she’ll got to jail for being a prostitute. The deal must be made implicit and people indeed do so implicitly. Read sugar daddy http://www.quora.com/Dating-Relationships/Does-the-sugar-daddy-sugar-baby-relationship-amount-to-prostitution