From your description it sounds as though your'e in Saigon...the "girls" you are meeting will most likely be prostitutes who prey off older men like yourself....my advice to you is to get in with a social crowd of expats and Vietnamese people..this way you will meet women who are decent and you can hear about them from their friends and judge their character.
A good Vietnamese girl will not want your money,although you will be expected to give a few hundred dollars a month to her for housekeeping, for which she will look after you big style.
It is illegal for a foreigner to shack up with a Vietnamese woman...so marriage will be on the cards eventually.
Take your time and use your brain and common sense when choosing a girl ,not your cock!
Good Luck Amigo!