@Cindy1226 There are hosts enrolled in the Open Homes program, who donate stays to people in emergency situations such as refugees fleeing Ukraine and Afghanistan, or people displaced by natural disasters. But of course, this program would be easy to abuse if anyone could simply create a blank profile and make up a heartrending story to get free housing. So the honest way to pursue placement assistance for your family would be to go through a charity that's dedicated to family support for cancer patients. Several of them do have arrangements with Airbnb Open Homes, though I'm not sure whether there's one specific to your family's situation.
Charity aside, many listings offer substantial monthly discounts, so putting the full time frame in a normal listing search might reveal an option that fits your budget. Honestly though, Airbnb is not a good venue for this, as it specializes in short vacation rentals. California hosts would be crazy to allow a 30-day occupancy to a stranger from the internet, as this is precisely how much time it takes to acquire right of tenancy and squat the property. I'd like to believe that your story is genuine - and I wish all the best to your niece if it is - but I hope you understand that some very well-known scams begin with messages exactly like yours, and hosts would be very unwise to take them at face value.