EDIT: as long as you get the money from western union first then your ok
hes paying you. (if it was the other way around its not safe) just make sure you get the MTCN number (money transfer number)..
go to western union give it to them and then they will give you the money. there are also fees (for him i belive) so make sure he sends enough i think its like 12.00 to make a western union for him