1. You can use this land record of R.T.C which had your grandfather's name and obtain Family Tree from the concerned revenue records, showing your name as the grandson of your grandfather, who was an agriculturist.
2. Based on the above, you can buy any other agricultural land.
3. Even though you are not an agriculturist now, but you are a descendent of agriculturists' family and you can say that you too and is an agriculturist.
4. Since your income from non-agricultural sources is less than Rs. 25 Lakhs and moreover you belong to erstwhile agriculturists'family, legally there is no hindrance for you to purchase agricultural land and it's not mandatory to have agricultural land in one's name only to buy agricultural land in Karnataka and if your forefathers' were agriculturists, then you will also be considered as an agriculturist.