Affordable housing has been a crisis in California, but a new report from the National Low Income Housing Coalition on Thursday found that the problem is nationwide with a shortage of 6.8 million rental homes affordable and available to extremely low-income renters, whose household incomes are at or below the poverty guideline or 30 percent of their area median income. The report highlights an across-the-nation, systemic shortage of rental housing for extremely low-income households. The report also points to the…