I think it’s all right to say income=business, but I would say “Our only income is from this business.” or “This business is our only source of income.” (putting “this business” at the beginning is just a matter of style, you don’t have to do it) “The only income we have is from this business.” or “This business is the only source of income we have.” Otherwise the sentences are fine. You can also say “How am I supposed to live like this?”