Deductions available from income from commercial property

1)A person has leased out commercial property @ Rs 30000/- per month. Rent is received after TDS deduction @ 10% = Rs 27000/- per month. What would be the taxable income and net tax payable with regard to this rent received? Please help and elaborate with calculations if possible. Also provide any ways of tax planning/saving regarding the same. 2)Is there any difference between computing tax on rental income from residential property and rental income from commercial property? Do they both fall under the same head "Income from House Property"? 3)How does one differentiate Residential Property from Commercial Property? What are the documents which show the difference between the two? 4)Is there any possibility that rental income from such a simple lease agreement can tantamount to profits/gains/income from profession or business? The assesee, who has given the property on rent, is a retired semi-literate person and is not involved in the activity going on in the leased premises.