A judgment will not prevent anyone from buying anything. If the judgment is secured against real property then it might prevent the sale of real property. You have to record the judgment at the auditor's office of the county in which the real property is located to secure it. For other states - you may have different procedures there.
It's not illegal to purchase property just because there's a judgment. Some lenders will ignore them, some don't find them, or it could have been a private loan. If you want to put a lien on their property in the other state, you will need to go through that state's procedure for registering a foreign judgment and then following what other procedures are necessary to secure your judgment.
The answers to these questions may be different depending on your individual circumstance and should not be considered as legal advice or the establishment of an attorney-client relationship.
Your question has been answered so I'll only add that you need to execute your judgment in the foreign state to protect your rights as a creditor. You can does this yourself (pro se) but it does require attention to detail a little bit of paperwork.
Stephen M. Dunne, Esq.
Dunne Law Offices, P.C.
1500 John F. Kennedy Boulevard
Two Penn Center, Suite 200
Philadelphia, PA 19102