Query about rented referrals in PTC sites.

I'm trying to renting some referrals, but I think it's not worth the money you invest in. The site doesn't garantee that they are active referrals, some sites let you recycle referrals, I mean that you can change a referral with a new one, but recycling has a cost. If you are a standard member, you gain a very lot percentage of the referrals earning. Finally, I think renting referral could be useful if you upgrade your account, but it also depends on the conditions of the site you are using.