Job offer to start tomorrow BUT ...?

Go in tomorrow as if you're ready for work, but ask to politely discuss the salary before you start. Explain to her that you think it's a little lower than you expected and would there be any chance of raising it to [insert salary here]. If she says no, just try to bargin a bit. At the end of the day, a job is a job in the economic climate we have at the moment. A job, even if it's not that well paid, is a lot better than claiming benefits!