You can purchase agricultural land for africultural purpose. Thier is no-problem. But, since you have to construct farm house, you need to change nature of land from agricultural to non-agricultural land. For which you need to give application to Tehsildar. However, that land has to be half kilo meter from last house of the concerned village. You will require NOC of all the other Governement departments such as Panchayat, Forest Department, Sarpanch, Patwari etc etc and as well as you will have to make it approved from Town Planning department. Only after NA and TP you can purchase land and make construction accordingly. However, if you are purchasing land in acres and showing it for agricultural purpose then you won't require all of this. Also, you can jointly purchase there is nor bar for joint purchase.