Hi,
Service Tax Purpose :
You say you will sublet a portion(obviuously at a lower rent than the portion let out to independent tenant).Now, how will you substantiate the lower rent consideration whereas for the other portion you shall be receiving higher consideration ? This case may fall under "short levy-short paid" of service tax which involves penalties, and you may receive a showcause from Service Tax officer, after which you may not be able to substantiate your stand, since apparently it will emerge as an activity to avoid the levy of Service Tax.
Income Tax Purpose :
Section 27 of Income Tax Act asks the assessee to pay tax on income from house property where the income is diverted without transfer of property.So, there will be different taxable turnovers.
Practically and technically your planning may not work if you are caught (taken up for scrutiny in either of the law).Until one is not caught, everything is good.