Link building agencies sell the one part of search work that cannot be produced on demand: references from other people's websites. That scarcity is why the category exists, why it is expensive, and why it attracts more shortcuts than any other corner of the industry. The distance between a placement earned because the content deserved it and a link bought quietly on a site that sells them is invisible in a monthly report and very visible to a search engine. This guide explains what these agencies actually deliver, where the risk sits, what moves the price, and how to check a candidate against live evidence rather than a portfolio slide.
What is actually being sold
Four models dominate, and they are not equivalent. Digital public relations produces genuine coverage by giving journalists something worth writing about, usually original data or a strong story; it is the most expensive, the least predictable, and the only one that produces links a competitor cannot simply buy too. Outreach based content placement pitches useful articles to relevant sites and earns a link inside them. Guest posting produces an article on someone else's site with a link back, and quality ranges from genuinely editorial to a network of sites that exist to sell placements. Niche edits, meaning a link inserted into an existing published article, are the model most likely to involve payment to the host site. Ask a candidate which of the four they run, in what proportion, and whether money ever changes hands with the publisher. The answer decides everything else.
Where the policy risk sits
Google's spam policies treat link schemes, including buying or selling links that pass ranking signals, as a violation, and the documented remedy is to qualify such links with the sponsored or nofollow attribute so they do not pass signals. Google's guidance on qualifying outbound links describes the attributes and when to use them. The practical consequence for a buyer is that a paid link which is not qualified is a policy breach carried out on your domain, by a vendor, that you will still own after the contract ends. This is not an argument against ever paying for placement; advertising and sponsorship are legitimate when disclosed and qualified. It is an argument for knowing which of your links are paid, because an agency that will not tell you has made the decision on your behalf and has kept the upside.
What moves the price
Most agencies price either per link, with the rate set by the metrics of the host site, or as a monthly retainer with a target volume. Per link pricing rises steeply with the authority and traffic of the host and with topical relevance, since a genuinely relevant site in a narrow industry is scarcer than a general lifestyle blog. Retainers are driven by how much original content or data the programme has to produce, because digital public relations costs money before it earns anything. Beware volume pricing that seems disconnected from difficulty: a low cost per link at high volume almost always means a network or a marketplace. Ask what the quote assumes about relevance, about whether the host site sells placements, and about how many links are actually expected to be live and indexed at the end of the month rather than merely reported.
How to vet an agency on live evidence
Ask for ten links placed in the last ninety days for clients in any industry, with live URLs, then open every one. You are checking four things: is the link still there, is the article about something a reader would plausibly want, does the host site look like a publication rather than a link inventory, and does the site carry dozens of similar outbound links to unrelated businesses. Ask what proportion of placements involved payment to the publisher and how those are qualified. Ask what they would refuse to do, because a candidate with no boundary is a liability. Ask how they report: live URL, date, host, whether it is followed or qualified. Finally, ask what happens to the links if you leave. Any agency that can remove them on exit has been renting them to you. Buyers weighing this against a broader programme should compare link building companies on exactly these same live checks.
Questions people ask about link building agencies
Are paid links always a problem?
Paid placement is legitimate when it is disclosed and qualified with the sponsored or nofollow attribute, which is what Google's documentation asks for. The problem is paid links presented as editorial and left unqualified, because that is a policy breach recorded on your domain. The question to ask a vendor is not whether they pay, but which links are paid and how they are marked.
How many links do we need?
There is no target number. What matters is the gap between your site and the sites currently ranking for the queries you want, in relevance as much as in volume. An agency that opens with a monthly quota rather than an analysis of that gap is selling a production line. Ask what the number is based on and what happens when the gap closes.
How long until links affect rankings?
Links have to be discovered and the effect is cumulative rather than immediate, so expect a lag of weeks to months and judge a programme over quarters. Any agency showing a ranking jump the week after a placement is presenting a coincidence. Ask for a live URL list each month and track the movement of target pages over a longer window.
Should we buy links or produce content that earns them?
Earned links are cheaper over time and impossible for a competitor to copy, but they need something genuinely worth citing, usually original data or a resource nobody else has published. Outreach programmes work best when there is such an asset to pitch. Buying placements is faster and does not compound, and it carries the policy risk described above.