Merely showing house property as stock in trade , rent income does not fall under Business income.
As per your query if it's single house property then rent income will be under the head Income from house property.
Besides, thanks to the judiciary, over time and after many cases, certain key principles have emerged as templates for characterisation of rental income under the head PGBP.
House PROPERTY HELD AS STOCK IN TRADE . SHAIKH YIU HAVE NOT MENTIONED WHETHER RENT RECEIVED FROM HOUSE PROPERTY AS STOCK IN TRADE IS TAXABLE UNDER WHICH HEAD : HOUSE PROPERTY HELD AS STOCK IN TRADE IS USED FOR BUSINESS PURPOSE. SO IT IS SHOWN UNDER BUSINESS INCOME. MERELY RENT INCOME IS GROUPED UNDER HOUSE PROPERTY. BUT SINCE THE ASSESSE IS USING IT FOR THE PURPOSE OF BUSINESS .