A common problem is that communities where you can say whatever (after moderation of course) will say things advertisers don't want next to their ads. An extreme example is 4chan, but another one is YouTube. A lot of advertisers pulled out of YouTube because their ads appeared before a video of someone making a racist joke[1].
[1] In YouTube's case it mostly hurt content creators, not Google.
I wonder if this is just something old fashioned ad companies will have to grow out of. Internet advertising isn't like e.g. advertising on TV before hand chosen shows.
I am not personally familiar with growthhackers.com nor Product Hunt.
1. Promoted posts, inline but called out to some extent.
2. Job posts. In HN's case, these are combined but there is also the "Jobs" page in the nav up top.
3. Regular ad network stuff as well. (Example Adsense, Carbon, etc)
4. Merch for sale
5. Paid mobile app
In the case of Reddit, they also do: Gold status which unlocks a few non important things
In general though, most of the sites have some kind of semi-hidden posts among the others that are actually advertisements.
There is one currently on the HN front page for "Etleap Is Hiring Data Engineers..." No submitter, no upvote arrow, no comment ability, but it's at #6.
Also, HN is a special case because it's probably cheap and could be funded by any YC member's pocket.
I think if you are going to build something like that, the strategy is to build a site that has value first and monetize later.