Definitely want to try my hand in this. I don't know anything about SEO and marketing though. Where could one learn?
And of course if you're looking to buy a site, whether on Flippa or elsewhere, you'll want to ask about any recent webspam action notifications from Google, as well as ask about any traffic trends in case the traffic to the site has gone down recently.
You have to love writing, what you are writing about, self/product promotion and project management like outsourcing tedious SEO things for cheap otherwise it will rarely amount to much.
If you are a developer and love these things, then sure it would be great if you could spend an extra hour or two for some months to make $36k in addition to a regular income, but I would say the kind of effort and results achieved by OP is an outlier. YMMV even if you have all the skills.
It's INCREDIBLY hard to get a blog to a profitable state, despite the fact that many people make it sound like a walk in the park. In fact, most successful bloggers will tell you it takes years of doing everything right to really get there. Not trying to be discouraging, just a little more realistic than this article.
If you really have the passion to start and stick with a blog, I'd definitely recommend these two books:
Blog Inc: http://www.amazon.com/Blog-Inc-Blogging-Passion-Community/dp...
and
Pro Blogger, Blogging Your way to a 6-Figure Income: http://www.amazon.com/ProBlogger-Secrets-Blogging-Six-Figure...
Another is their SEO Report Card from a different angle: http://googlewebmastercentral.blogspot.com/2010/03/googles-s...
Moz (SEOmoz) provides another good source of info here: http://moz.com/beginners-guide-to-seo
This seems harder — making apps is more time-consuming and a less common skill than copy-pasting pictures of cupcakes.
It also seems less straightforward — the concept of "figure out what lots of people are talking about, make blog on topic, stick ads on it and let Google bring in visitors" is pretty simple, whereas I have no idea what the equivalent is for apps.
I think that's why it's easier to generate passive income.
Because of that, it's probably easier to generate income from apps because the market is not as saturated as niche-wordpress-blogs.
Just look for someone posting this comment on HN and partner up:
Wow, there is money in this? Why am I wasting time working on legitimate and difficult products? I'm a fantastic Internet marketer, and this seems like something slapped together very easily.