Links remain a real signal and the market for them is full of practices search engines explicitly describe as violations. The distinction is not subtle: a link earned because something was worth citing is an outcome, and a link bought or exchanged to pass ranking signals is a scheme. A programme has to be built so that the first happens routinely.
What search engines actually prohibit
Published spam policies name link schemes directly, including buying or selling links that pass ranking signals, excessive exchanges, and large scale article or guest posting campaigns with keyword rich anchors. Paid placements are expected to be marked so they do not pass signals. A supplier who will not say how links are obtained is telling you something.
Assets are what make links repeatable
Original research, a genuinely useful tool, a dataset others want to cite, or expertise a journalist needs. Outreach without an asset is asking a stranger for a favour, which is why it converts poorly and why it drifts toward payment. Building the asset first is what turns outreach from begging into an offer.
Judge relevance and traffic, not counts
A link count is a poor measure. What matters is whether the linking page is relevant, whether real people read it, and whether the link is editorially given. One citation from a publication your buyers read is worth more than dozens from sites that exist to host links, and the second category carries risk as well as no benefit.
Questions that reveal the method
Ask for examples of links placed last quarter and look at the pages themselves. Ask whether money or goods change hands, how anchors are chosen, and whether placements are marked as sponsored. Ask what they would do if a client's page was not worth linking to. The honest answer is that they would fix the page first.
Questions people ask about link building program
Is paying for links ever acceptable?
Paying for placement is a legitimate advertising purchase when it is marked so it does not pass ranking signals. Paying for a link intended to pass signals is what the published policies name as a scheme, whatever it is called on the invoice.
How many links does a site need?
There is no threshold. What matters is the competitive context and the quality of what points at you. A supplier quoting a monthly quantity is selling volume, which is the shape most likely to drift into schemes.
What about guest posting?
Writing genuinely for a publication's audience is normal. Producing articles at scale mainly to place keyword rich links is named as a scheme. The test is whether the piece would exist if the link were removed.
How long before a link programme shows results?
Months rather than weeks, and it compounds. That timeline is precisely why buyers are tempted by suppliers promising fast volume, and why those suppliers are the risky ones.