Yes, none of that is problematic. You should just make sure you're not indiscriminately linking to third parties who pay for the privilege. In your case nofollo

Yes, none of that is problematic. You should just make sure you're not indiscriminately linking to third parties who pay for the privilege. In your case nofollow would be very simple and would prevent any damage. Quality content is awesome and I'm sure your site is great, but Google's thought process here is that your site's reputation should only be handed on to sites that earn it organically (e.g. not through their buying it). It's really for your own benefit, with the way PageRank works your outgoing links are votes that are as powerful as your page's reputation is good. If you link to bad sites your page's reputation takes a hit and thus your PageRank goes down. If I pay you to vouch for me (e.g. link to me) that only means that I have money. If you vouch for me without any money that's a much better signal that I have quality content.