Hello, Laura! I love all of your very practical questions. I'll try to answer them briefly here. I'm also writing a FAQ to follow up this article since I've received so many wonderful questions.

Let's see...you only need one website in a good niche, if you nail the keyword research and monetization. I have three websites to spread the risk in case one of them tanks.

You can earn money for years and years, but you will need to keep adding some content. Yes, you will need to eventually refresh some old articles if the information gets too old and out of date.

If you write "evergreen" articles, you should be set for a long time.

For the URL, I like to go broad so that I can write about lots of sub-topics in that broad category. However, I tend to focus on one subcategory at at time to create topical authority with Google.

For example, if I choose a URL like "BackyardGuru" then I can write about anything that has to do with the backyard. Normally, I would write 100-1,000 or more articles about one thing, such as Grills. When I run out of those topics, I'll switch to something else related to the backyard.

I hope this helps!