I have two main sites that provide most of our income. They are on separate servers hosted in different locations - one is a Drupal and other other is WP.
We do have a few other websites, like a recipe site. I started that when my wife and I would spend a lot of time cooking something special. Why not share it? I also have a forum.
My wife also has a decorating site, but I don't think she spends enough time on it - there are only so many hours in a day. She has taken an interest in apps lately. We will see if anything develops out of that.
We make our living from this business. It pays our mortgage, health insurance and everything. They are my baby and I spend nearly all my time thinking and working on them.
We have other sites that we experimented with and may not renew the domain. I even created a content farm. LOL I stopped accepting submissions because it started taking too much time and they don't pay that much.
MS, you mentioned upgrading. The Drupal site is pretty old and if we do update it, we need to change the theme or it will crash. A lot of people add plug-ins to their WP site. Remember, if you update your site you need to make sure all of the plug-ins will work with the new version, otherwise your site will crash.
Unless you are hosting your own site, upgrades are important. What if the host upgrades the PHP or MySQL? This could cause problems and even crash your site.
Here is something Aristotle said:
Actually, from my own experiences, I think you have some big advantages when you're trying to rank a small site. For example, you have more time to spend on each page and develop its content.
I like your way of thinking. I also think Google's results will be best if their algorithm doesn't judge pages on a site-wide basis. But, they are the ones that have to program their algo.
Here are some ideas to improve a site:
1) Google provides maps, videos (YouTube), calendars and much more. I heard Eric Schmidt once describe Google as a publisher's solution. For the most part, their solutions are free - even Blogger. Take advantage of their free tools to make your site better.
2) Learn graphics programs. Improve the graphics for your pages. Right now I am reading a tutorial for 3-D animation - mostly just for modeling.
3) Try to make your site / page better than the top ranking page in your SERPS.
4) Also, don't forget about social media - follow buttons, like etc. But the content should come first, IMO.
Those are my thoughts on this topic.