When can I tell if hes serious ?

Ok if meet a guy on the train he works on the train he came up to me started talking to me not even for long then he asked my number. He keeps telling me how beautyfull I am and that he wants to get to know me an so on no that hes got my number he starts getting kinki on msn I told him why is he getting rude with me so early? Then he says hes not. He keeps doing it. Now I asked him what do he want with me he said ok I do want my dik inside you but I want to know if you want a relationship with me because he wants a relationship with me he even say what he wants one day maybe a family kids a house and get married if so then I get a txt from him when he say I musnt tease him I dont even know what he means he say I tease him with my body just becoz I wear singlets tank tops. So I said to him I need to get to know him better so he asks me how long how many months weeks is it gona take him to prove me hes serious. So I said 5months maybe so he say no its too long for him to prove to me. So I said ok well I dont know why but everytime I meet someone they only wants sex and that kinda drives me away from that person. So he replys to me saying well miss its upto you to make the decission about wether you would want me in your life or not you already no thoughts and feelings on that subject what mor can I say? So I tell him im sorry but I just wanna be friends and if not then fine. So he replys ok friends it is then ill chat to you tonite have a gr8 day. Thats how the convo ended so will see tonite if he gets back. What do you guys think on that does he seem serious or just someone who wants to get laid?