Companies are starting to offer me $ for in text links but I've heard that can potentially hurt my PR and/or ranking. If I do these in a relevant blog post (so they are part of the content and not just sitting there somewhere) is that okay?
Google doesn't really penalize you for inbound links assuming you can't control other websites linking to yours. But, this is not the case with external links in your site. You will be penalized for unrelated links. Say you have a website dedicated to children's books, and you sell a link to a pharmacy site with an anchor like "Buy Viagra", I can guarantee your rankings will plummet in Google serps. With this, I'm not saying it's not impossible to sell links, just keep them related to your sites content. Never sell a link that you are not comfortable with for your visitors and you should be fine.