They cannot legally work without an approved EAD; doing so would violate immigration status.

They can apply for an H-4 EAD if the H-1B spouse has an approved I-140 or is on AC21 extension.

Starting a business is possible, but they cannot work for it until they have the EAD.

If they want immediate work, they must switch to a visa category that allows employment (e.g., H-1B, L-1).