Therese said:
"Yet the land income, as well as house renting income, was submitted to taxes, which in Regency times, did not affect other kinds of income."

I am not an expert on taxation in JA's time, but I do know that Income Tax was levied on all forms of income between 1799 and 1815 to pay for the Napoleonic wars. See the link below for a bit more info on this.

When you refer to taxation levied on land as opposed to other types of income, I wonder if you are thinking of Tithes.
Tithes were a form of local taxation which paid for the local Anglican clergyman. This was a very old form of taxation which in theory was a proportion of agricultural produce. The system had become hideously muddled by the Regency period, and was reformed in the late 1830s