You know Google will ignore most of these links, as somebody with a ton of sites I've tried a lot and I can say 99.9% of these links don't move the needle,
If somebody is openly selling links online, do you think Google won't notice, Do you think they won't have domains with a large amount of outbound links?
That being said I understand we all desperately want to rank and yes backlinks are a part of that, I however firmly believe it's not as big a part as it used to be. I've seen numerous times where new websites will compete and sometimes outrank ones with more links because of what I assume is better content. (for certain search phrases.)
So you have the above saying make quality content and also making quality content and promoting it can get you links, it's not easy but it does happen.
There are vendors out there who sell proper links, but they come at a price and you are always rolling the dice with them.
If you could get a link that brings referral traffic that is absolute gold. Those are the ones you should look for.
For example, we sponsor hosting for schools, and in turn, we get some backlinks. A lot of the parents of the kids in those schools are business owners or want to know more about getting a website going. They like the school website and come to us. We get backlinks we get traffic, sure you can argue we pay for the backlinks... you can also pay for Google Ads.
There are ways but all in all wouldn't rely on link gigs.