It depends on a lot of things. Something self-hosted would just cost the power and Internet you are already paying for but if you’re renting the hosting and maybe even get development for your site it could cost a ton.

None, like the porn posts need to be clicked on to show the picture so it’s not really an issue and even if it was visible by default I wouldn’t mind, it’s just porn. I would block gore but I haven’t come across that yet.