Independent Contractor at Startup Needs Advice

It sounds like you deserve to get a good amount of equity, but you may be overestimating how much leverage you have. You may think you're unexpendable, but the founders may not agree.

Focusing on the the work you've done so far is a mistake, because from their perspective you've already signed a contract to do that work for a given amount of compensation.

I would emphasize the value you're going to bring to the publishing startup in the coming months and years. If you can persuade the founders that the startup is 15% more valuable with you in it, they may give you 7% equity in exchange.

If you set an ultimatum that you want X or you'll walk, be prepared to actually walk.

I agree with the abovementioned poster. Writing is generally seen as expendable unless you posses your own brand or followers or expertise that nobody else has.

If your writing is able to draw traffic you can position that as an asset but otherwise I'm not sure you have a lot of leverage.

"I believe that I should not only ask for more money, but also seek some kind of equity in the company." Sorry to break it to you but you're not entitled to anything. You're working, and most importantly getting paid, regardless of the outcome of the company.

Whilst you may have contributed to the success of a business, generally speaking you haven't done anything they didn't pay you for (at a price you already both agreed!) and thus they could have paid someone else to do. Your entitled attitude would get you fired immediately from my start-up. Instead, be greatful you have the opportunity to work with the company as it grows, stay loyal and keep your feet on the ground and you should be rewarded - if after some time you don't feel the reward is there then that is the time to justify your worth (salary) and if that still doesn't change anything then go find work were the value you are given matches the value you provide.