Is having a real marriage and wanting a green card legal?

[moh]

I'm from Canada and I would like to become a US Citizen.

I think getting married and having kids would be great, and a common answer to becoming an American is 'just get married!'.

It is also common to hear that marrying for a green card is illegal.

On the other hand, being a mail order bride is legal.

Is it legal to be a mail order husband, or to look for a real marriage to an American, if a strong motivation is to become an American and get a green card?

Or in order for it to be legal does the person have to marry only for love and to essentially have no interest in getting a green card?

I'm also wondering if it is okay to visit the US, looking for love?

[immihelp]

As long you are looking for a real and authentic marriage, it is no problem if it also comes with the benefit of a green card.