Having stayed at home with my eldest for a while, my opinion on being a SAHM is that it's very bad idea in the society we live in.
In this society, looking after children is not counted as work - you don't get any pay, any recognition and minimal pension contributions. Staying at home to look after children puts a parent in a very vulnerable position. That absolutely shouldn't be the case - raising the next generation should not be seen as a valueless act - but it is. That's based in misogyny of course - it's women's work and therefore must be done in the background without interfering with the Important Work that men do. The very idea of paying someone to raise the future of the human race is seen as ridiculous - women are supposed to do it for free, out of love and other such lofty ideals.
In that context, IMO, being SAHM is risky. If you have at least some work history, if things go wrong - you break up with your partner, your partner dies or loses their job - then you have some backup, some way of keeping things running. If you've had years at home, that's frowned up on in so many job situations - getting a job is very hard, even just from the point of view of finding one in the first place.
It should absolutely be possible for a parent to stay at home with children and for it to be a positive choice for everyone. It often is great for the children and great for the working parent, who have someone constantly at home organising everything and making their lives easier. But for the SAHP it's a really shit deal. Apart from the financial risks, I've seen too many SAHMs lose their identity and become the person the family takes for granted - the dogsbody everyone relies on to be there at all times with no personal needs or dreams of their own. Being very focused on the family works when the children are small but what happens when they grow up and become independent? Many mothers find their stride again, get back into work, reclaim their own place, but many (and I know quite a few) don't - they're lost, no one sees them, they don't have a clue how to be anything other than the person their family relies on. I've also seen situations where, when the SAHM tries to get her own life back, the family gives her hell - she's not supposed to need or want anything and her desires are very inconvenient. When my best friend was going back to work after being a SAHM for about 7 years she talked about finding a job that fit in around school and not having too much of a commute. I said to her 'you've been the one accommodating everyone for years, why do you have to jump through so many hoops, why can't your DH change his hours or make sure he can do schools runs etc?' She had genuinely not even considered that her DH had some responsibility and that she could and should look for a job that she actually wanted to do rather than just one that suited everyone else.
It's so easy to become nothing and nobody in a world that doesn't value mothers and the work they do. It'd be great if that could change.