Has it been determined that repeated stress and inability to find jobs cause one to develop schizophrenia?

No. Another reality is that if someone is developing schizophrenia, one is likely to feel stressed, and may have trouble finding or keeping jobs.
No. While repeated stress and unemployment can lead to a number of psychiatric problems, like depression and anxiety, schizophrenia is not one of them. However, if you have schizophrenia, your symptoms can worsen if you are under stress.
Yes and no. Schizophrenia is genetically loaded and varying degrees of severity and stress of any kind can precipitate the overt illness. Repeated stress and inability to find jobs could cause symptoms of latent schizophrenia to occur. The illness was likely there and just not overt. So if it develops the stress can cause a genetic predisposition to show up, not directly cause it.