Have you looked critically at your expenses though? Part of the power of a stay at home spouse/parent is to reduce other costs. Not just day care, but so many things. Don't limit yourself to gender stereotypes either- car repair, lawn care, gardening, canning, cooking, sweat equity if you own your home, etc etc. There are so many things you can do to add value that don't give you a W-2.
^^ This.
I assume you mention $30k is because you're making $30k, not a detailed set of calculations based on what you won't be doing (if wrong, sorry... that's usually what people start out assuming).
My wife is a stay at home mom with our 11 month old, and we'd been planning on this for a while, but she's a huge contributor to the family budget, mostly because she's
better at not spending money than I am. By a
LOT.
Your car use should drop a lot if you're no longer commuting, especially if you can walk to some stores. Make sure you call your insurance to let them know it's no longer a daily commuter - that can make a big difference in insurance costs!
It sounds like you're using some sort of daycare now? That goes away entirely, cost-wise.
I'm not sure what your family eats, but my wife has been cooking pretty much everything from scratch, often in bulk, and she spends less to feed both of us and the kiddo than I spent to feed myself post-grad-school, and we eat a lot better. Soups, stews, and stir fry are amazingly cheap, incredibly tasty, and don't require much time from her. If you're doing this, get a good set of knives - it makes a huge difference.
Cloth diapers save a good bit, but require doing laundry regularly - not a problem with a parent staying at home! With two kids, it's going to be well worth the hassle.
Don't look at it from the "How can I bring in money?" point of view - look at it from the other side. "How can I help reduce our expenses so we don't need the extra money?"
TBH, depending on what your husband does, you working may be about a wash. Between taxes, commuting, and childcare, I think we'd be behind financially if my wife went back to work (trained as a teacher, was working as a secretary, bringing home about $30k). And you'd have to pay for *two* kids in childcare.
If you're willing to share more details, I suspect people could offer some more concrete suggestions.