Link renting can drive important direct traffic. The first things you need to know about a site you force rent links from are:

what is the class level of the traffic?

how associated is this audience to your product?

how much traffic does the site obtain?

What is the Quality height of the Traffic?

If you do not see any quality inbound links that could designate a problem: or they could get the majority of their traffic from pay-per-click ads. Whatever the case, if you are going to use money renting links for traffic, make convinced you know where their traffic comes from.