Here is some guidelines...

1) When only they bank in then only you deliver the product to them.

2) Most of this con people will trying to make "small" purchase with you in order to gain your trust.

3) After a while where you "trusted" them, they will try to order a big portion without paying you first.

4) The end they disappear... and you lost your stock without being paid...

Just follow the simple rules, dont ever trust them. Money comes then only stock deliver... You wont get wrong any how...