Your existing contract determines the rights you would have in these circumstances. If, as you represent, the seller has broken the contract by allowing a tenant to remain in the property and cause damages, you should look to your contract terms to determine how you could enforce your part of the bargain.
Your best bet would be to take your contract to an attorney in your area who is familiar with rental property real estate transactions (I'm assuming from your description that this is what you are purchasing). Check online for your county's lawyer referral service, or go to the Pennsylvania Bar Association website at http://www.pabar.org/public/membership/lrsblurb.asp to find the closest agency to you.
Of course, as with all of my online answers, my advice is limited by the brevity of your question and the facts provided. Additional information would be required to provide definitive legal advice, so this answer isn't intended to, and does not, create an attorney-client relationship.
If you feel this answer has been helpful, please consider checking the "good answer" box below.
I agree with Attorney Taminini, who is a regular contributor to the Avvo forum.
Consult with an attorney.
PS: Please mark this as a best answer if it is most helpful to you.
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