What should an american woman know about dating a nigerian man...

What should an american woman know about dating a nigerian man, wouldn't he prefer to be with someone who is familar with his own culture?  He tends to avoid other nigerians in general and says that women were he is from are alot of trouble if you bring them to a country like the U.S.  This sounds ridiculous to me.
Just looking for advice.  I have never known a nigerian man before, but I have been dating one for almost a year now.  Initially he told me he already had his papers or green card, but recently he fessed up and told me it was all still up in the air(he is here legally sponsered by his employer).  Then he talks about being home sick and wanting to go back, if this is the case then why bother becoming a U.S. resident?  He has been asking me if I would want to visit or possible relocate there at some point in the future because his parents are getting old.  I'm really confused, he says he only came here to get his master's degree, but while in school he applied for asylum. Should I be concerned about his intentions as far as trying to get me out of the country?  Is he using me to get his green card?  He really seems genuine to me and I don't mind helping him if thats the case, but I don't want to get myself in one of those nightmare situations you read about.  I thought maybe getting input from other people more familar with this country's culture could give me some insight.