The Federal and State tax rate for a non resident alien would be the same for a non resident as it would be for a resident. The net income after deducting all allowable deductions including depreciation would be subject to ordinary income tax. Since our income tax system is progressive, the rate would depend on the total amount of income received. Only income earned in this country by the non resident alien would be subject to tax. An income tax return should be filed by the non resident each year. The rental income is considered to be passive income and is not subject to social security tax.
When the property is sold the buyer will be required to withhold 10% of the sale price for the IRS, and 3 and1/3% for the CA Franchise Tax Board. The non resident should still file income tax returns with the IRS and state. If the amount of tax owed is less than the amount withheld, the excess will be refunded.