usually, the folks running these freelance services will have usage of a private blog network (PBN), which happens to be a community of websites they individual that they can easily spot one-way links on.
Enroll in https://aishagmlq449392.thenerdsblog.com/34867348/how-much-you-need-to-expect-you-ll-pay-for-a-good-web-traffic-sites