Offer your thoughts or opinion on the input financial query or topic using your financial background.

How do I fold side-income into our budget so my husband doesn't know? 
I doubt that it is possible to keep something like this secret from your husband forever. If you get away with it once, I'd guess you'll probably try it again, and sooner or later he'll find out. He'll notice that things show up in the house that aren't accounted for in the budget, or he'll see a statement from your secret bank account, or one of your friends will carelessly say something about it when he's around, etc. I found out about some of my ex-wife's secret finances when she wasn't home one day, I got the mail, and found a credit card bill for an account I knew nothing about. If the preconditions on the question are that you're not going to tell him the truth (and you're not going to get a divorce), I think the only realistic answer is that there is no way of keeping this secret with a high probability of success.