Cardi B would make a helluva hookup artist ... just ask our photog!!!

We got the rapper leaving Ace of Diamonds Monday night and our guy was minding his own business (not really) when, out of nowhere, Cardi dished some priceless advice about how to get laid on Rodeo Drive. Best of all, her plan is totally affordable ... and she offers a 100% money back guarantee!

Check it out ... Cardi's also got a strong take on celibacy before marriage. Hint: she ain't buying the cow without tasting the milk.