1) before purchase of any property contact a local lawyer .
2) obtain title clearance certificate that title is clear and marketable and free from encumbrances
3) check whether building plans have been sanctioned by muncipal corporation
4) ask for inspection of building commencement certificate .
5) once builder has completed construction as per sanctioned plans builder will get occupation certificate from muncipal corporation .
6) if builder from whom you are purchasing property is not a reputed builder from Bangalore dont invest your hard earned money unless builder has obtained OC
7) to be on safer side please check whether project is pre approved by bank . obtain loan for purchase of flat .