The only thing to try to investment website are legit or paying is to invest or if your friend tested it like he already investment or put money on the investment website but always invest once and never do it agian for sure that hyip are going to be scam
Even if your friends are having success with investing to these hyip sites, there is still come a time that these sites will run all of the money invested to their sites. Look at hashocean, they operated for a very long time and with these people who invested in the site think that it is not hyip and recommend it to their friends only to find out that it is indeed a hyip and scam site.