I really don’t get the whole don’t ever buy backlinks message from the SEO community.
If you employ an agency, and they provide you with backlinks, then you give them money, whatever way you want to look at you are buying backlinks.
It’s more the quality of the link that you should be concerned about. There is nothing inherently wrong with ‘buying backlinks’, it is one of the pillars that hold up the SEO industry.
There is a demand for backlinks to increase SERP, SEO agencies can supply them, its simple economics.
Obviously agencies do a lot more than simply supply backlinks, but every agency is going include them any monthly package they sell to their clients.
Most businesses don’t have the luxury of producing great content and then waiting months/years for people to link to it. If they did they would go bust in the meantime.
But don’t buy spammy, worthless, outdated pure black hat links. You can definitely say don’t buy those links.
If you have the budget, employ an agency. But to get decent results you are looking at thousands per month for most industries.
If you have the time, try do it yourself. Get some high quality content together, then google the life out of link building. Read every article you can get your hands on. Then try follow those techniques.