to know if someone is your friend or if he/she is just lying to you, you first need to know if you are lying to yourself.
most people who "want" something will consciously or unconsciously accept/interpret even the faintest sign as validation that their wish has come true. and they will continue to lie to themselves and to fight of evidence that indicates what "really" is going on.
nobody can fool YOU, if you don't support the process one way or another.
if you really are rich: don't spend money on friends, spend it on business. if you are rich you can buy the thing that really "buys" friends: "time". spend time on your friends. see if you trust them, and if they trust you.
if you or they don't, tell them about it! people who trust each other (or want to trust each other) tell the truth, regardless of how painful it might be.
otherwise they or you will end up emotionaly bankcrupt, when you think you have someone to rely on, but really don't.
this is true for any kind of friendship or relationship.