There are lots of people who advertising there site to others for invest their.There are several types of side such as hyip,ptc and so more.I personally think that this site isn't safe for investment.If you invest then you gonna lost your money.
First, all HYIP/MLM are ponzi schemes where new investors' money is used to pay the old investors. They come and go everyday and people get scammed by them everyday as well.
Second, Is it profitable? Yes and No. Mostly No.
The risk associated with these are very high but there are some people who hunt these new HYIPs everyday and have a promotional channel on facebook or telegram where they have a bunch of brain-dead "happy shills" who will join in that person's downline immediately on that day. Maybe they will not invest but among 1000 users possibly one or two naive newbie will put in 100$ in it. Thats good enough referral commission for the original referrer and this is how these "scams" get promoted and propagated; the person who promoted them gets his cut and person who invested gets stuck there: This guy may luckily end up making some money if they manage to get enough referrals or will be short of time to withdraw because by that time the site will go down and disappear and so will his money.
About PTC, most are just a waste of time in my opinion, you might think otherwise. If you are trying to use them to make some quick bucks, dont buy any ad-pack or bought referrals. They are a waste of money and you wont be able to get them back if you consider them as investment into the site.