Any suggestions on how to earn money even if you're staying at home as full-time housewife?

You can do anything that you are skilled in. I mean the best thing to start is what you have studied. If you have done any course in baking or otherwise also you are a good cook, you can start a tiffin service, or can start a food truck. If you know knitting, you can knit range of baby stuff and have your own online kids shopping website and sell your stuff on that. If you are a good writer, you can write for various online sites. May be some travel, beauty or lifestyle pieces. You can also start your own babysitting thing at your home. Or can take tuitions.