There are no fixed cut off for private medical seats. You can easily get them if you have qualified NEET. 

Hey.

For admission in a private medical college for MBBS the cut off will vary from state  to state and college to college. Some top private medical colleges have higher cut off than government colleges.
But if you score around the range of 300-450, you would have fair chances for admission in a Private colleges through the state quota. As you want to know the minimum cut off, So you must score atleast above 300 to get admission in a private medical college.

Best of luck!