Working in different countries

I am a Canadian living in the US. My visa will be up at the end of April and there will be a two month gap between before the next work permit comes through. I will leave my full time position, but can I still remain here living with my American husband, doing freelance work, but send my American clients bills from my home address in Canada?

Does anyone have experience with this? I image it would be similar if someone went to Spain for a summer or something with only a tourist visa and kept working — sending clients bills from their home address.