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.
The Law Office of Christopher Barrett Fay, 1325 Spruce St., Philadelphia, PA 19107, email@example.com, (267) 519-2719, www.cfaylaw.com. LEGAL DISCLAIMER: The law changes frequently, and the material on this website is for general information purposes only and neither constitutes nor is intended to be legal advice. You should not act based upon this general information nor without seeking legal counsel regarding your specific legal matter. The outcome of every case is dependent on the specific facts and legal circumstances of each individual case. Any client reviews or attorney endorsements posted on this website are solely the opinion of that person and should not be construed as representative of the results you might expect to receive in your specific legal matter. No one can offer a review or endorsement concerning the type or quality of legal work they received in relation to the type or quality of legal work that might be done for you if you become a client of this office. This website is not advertising. This website is not an offer to represent you, which can only be made after a consultation with one of our attorneys. This website and its feature to contact us do not create an attorney-client relationship between you and The Law Office of Christopher Barrett Fay or any of its attorneys. The Law Office of Christopher Barrett Fay practices law only in the states of Pennsylvania and New Jersey. The Law Office of Christopher Barrett Fay does not intend to practice in any other jurisdictions where it is not licensed. The firm does not seek to represent anyone viewing this website in other jurisdictions, and the website may not comply with the laws and ethical rules of states other than Pennsylvania and New Jersey. Pursuant to the requirements of U.S. Treasury Regulation Circular 230, any tax advice contained in this communication (including any attachments) is not intended to be used, and cannot be used to avoid penalties imposed under the United States Internal Revenue Code or to promote, market or recommend to another person any tax-related matter.