Link building is usually sold first because it is the most legible part of SEO: a number that goes up, delivered monthly, easy to invoice. It is also the part that is worthless until several other things are true, and the part where a bad supplier can do lasting damage rather than merely wasting money. Getting the order right saves most of the budget that businesses lose to this service.
Three things have to be true before links are worth buying
The site has to be crawlable and reasonably fast, the pages you want to rank have to exist and be genuinely about the thing, and the on-page work has to be done. Links amplify a page's ability to compete; they do not create it. Buying links for a page that does not deserve to rank is paying to make a weak page slightly less weak, which is the most expensive way to improve a website.
Ask which page each link is for, and expect a real answer
A supplier should be able to say, before starting, which specific pages need strength and why, based on what currently ranks for those terms. A program that acquires links to the home page or the blog because those are easiest to place is not aimed at anything. This one question separates suppliers who have analyzed your situation from suppliers running a standing process with your name on it.
The policy is public, so the method can be checked against it
Google's spam policies name link spam explicitly and include links exchanged for money, goods or services where they pass ranking signals. That is the standard, it is published, and any supplier can be asked to describe its method in its terms. The useful follow-up is what the supplier would refuse to do. A specific refusal is worth more than any assurance.
Internal links are free and usually neglected
Most sites carry pages that already have strength and do not pass it anywhere useful, because the internal linking follows the navigation rather than the priorities. Reviewing and fixing that costs a few days of somebody's attention and no acquisition budget at all. Any supplier proposing external link building without having looked at the internal structure has started in the wrong place.
What to do about the links you already have
Sites accumulate links from old agencies, directory submissions and growth experiments nobody remembers. Before adding, get the existing profile listed and classified by how each link came about. Sometimes the finding is that nothing needs doing, which is a useful thing to know for a few days of work. Sometimes it explains why nothing else has worked.
Questions people ask about SEO and link building
Is link building still necessary?
Links remain one of the signals search engines use, so in competitive commercial categories they still matter. What has changed is the returns on volume: a small number of genuinely earned links from places your buyers read is worth more than a large number acquired at scale, and the scaled version now carries risk it did not used to.
Can I do link building myself?
The most effective forms are largely in your control: publishing something worth citing, making sure partners and suppliers who mention you link properly, and claiming the places your business is already listed. Those are unglamorous and free. What is hard to do yourself is sustained outreach, which is mostly a relationships and persistence problem.
How many links should a campaign produce a month?
Any supplier quoting a monthly quota is describing a process rather than a plan, because the number of good opportunities is set by what you have to offer rather than by what you pay. Ask instead what will be produced that somebody would want to link to, and judge the program on that.
What should I do if I inherited bad links?
Start by classifying them rather than acting. Many are simply irrelevant and ignored. Where there is a pattern of links acquired through payment or exchange, that is worth addressing deliberately, with advice, rather than reflexively disavowing a long list. Removing good links by mistake is a real and common cost.