There is a ton of information on this forum and all across the web on starting websites... You are just going to have to find something that interests you (or even something that doesn't) and just jump in. One piece of advice that I will give you, is that you shouldn't be afraid of stepping out of your comfort zone. Some of my best earning sites are about topics that I am not particularly fond of. However, they bring me money, so it doesn't matter if I like them or not, if it brings me money, I am all there.
While it is awesome that you are taking the step to make some more money, you literally have to do your own research, find what works, implement it, then rinse and repeat. Like you said, no one is going to give you the step by step or even tell you what you should do, you really just have to find something and start doing it.
Best of luck to you and your wife.
Take it easy!