StjepHow do you tell a good friend, that the job offer they're super enthusiastic about, and intend to reshape their life around, is *riddled* with red flags, and that they shouldn't touch it with a 10-foot pole 
xbyte1024@stjepanlukac How good friend?
If you are too comfortable, you can just say your thoughts.
If you are not comfortable enough to be bold, you can ask if he/she noticed the red flags, pinpointing the most obvious ones and ask if it's worth taking such a big risk (probably talking also about the amount of risk).
Then you hope this works. The final decision is not yours anyway. There is not always something you can do.