I have meet a wonderful man from israel,we would like to be married soon how do we do this?GREEN CARD?

I am a USC w/ a son. this man asked me to marry him the other day. I am worried about the INS thinking it is for his green card. how do I go about proving it is for real? He has his ex-wife and 3 kids in another state that he sees when he is not on the road as he is a trucker. He will only spend the time he can with me, which is about 2 weeks out of the month. Very worried about the immigration laws. We love one another very much. I have never been married and would dearly like to do so. but I am scared that he is not a USC...Help any answers would be great thank you