vacant possession of buying property

No need to vacate them. Instead you give a notice to them for change of owner of the property and mode of payments rules etc. after possession of the property. 

'Buyer Beware' applies to property deals.

IT shall be appropriate to get proper legal opinion from a very able LOCAL senior counsel of unshakable repute and integrity specializing in revenue/property/civil/DRT/Rent matters and well versed with LOCAL applicable rules/laws and having successful track record…. and worth his/her salt , before signing or making payment.

This may cost some FEE but can defend long term interest and hard earned monies.

Obtain the legal opinion in writing and thereafter decide yourself.

It is better to get premises vacated, before buying.

Rest is your personal decision.