I actually did this in June to some extent. I became very interested in 3D Printing and launched a website dedicated to it in January. I wasn't making any money from it, just posting because I enjoyed it.

In June I had enough of the bullshit at my job I had been with over 5 years. I was managing the business and they hadn't paid me for almost 2 months, so I sent them my invoices for accounting purposes, paid myself and finished off my last 2 weeks there.

I became an Amazon Affiliate and invested a lot into promoting my website, taking out Reddit ads, Google AdWords, Facebook Ads, etc. with the intent of making it more well known outside of the niche circles. In just over 1 1/2 months, I have referred over $26,000 of sales to Amazon, meaning I make around $800/mo.

Sadly that isn't enough to live on so my hobby isn't sustainable at this point in time. It is however a nice side income, getting paid for something I was already doing for free anyways. I am working on my resume now as my funds are depleted and I need to find a job, however I do hope that eventually my website will be successful enough that I can pursue that full time, teaching others about my passion.