[cheap]

How long does the tenant have on the lease? If they have 30 days left, make the contract settlement 45 days and conditional upon the property being vacant, clean, neat tidy, with no damage. Be specific, carets cleaned, floors cleaned, bathrooms clean...

Have a comprehensive building inspection done pre tenant leaving and post tenant leaving, make sure you tell the inspector to look for all items no matter how minor. Any costs to make good to be the sellers responsibility or deducted from the contracted price.

Now this is important, once they've vacated change all the locks.

Let the seller and the agent sort it out. For all you know the tenant may not a have much of a bond and could abscond leaving the place wrecked. BTW Tenant laws are a joke and real estate agents can not be trusted to manage tenants.