Yes, housing is taxable, but you have to pay the tax from your salary, so that alone means 30% of salary must be saved to cover the 15% on both salary and housing, assuming your housing is similar to your salary, but more % if it is higher than your salary.
Yes, you have to pay last year's and next year's tax the first time you pay, so you have to have approximately double the cash on hand. All the banks offer cheap loans if you're short on cash, but that just means it will cost you more, and you still have to pay double (though divided into 2 payments that are 3 months apart or so).