Mortgages that go with the sale. Short sales and REO's. Former owners who refuse to vacate.
Deed transfers, ususally have unpaid back taxes and other issues that cannot be resolved.
City won't give certificate of occupancy because you did not kiss their ring or bow down to them and beg. You told the woman to get off the property and now she has a vendetta against you and won't sign certificate of occupancy.
Severe unseen damages such as water and sewage pipes, structure that require extensive and costly repairs.
Strange clauses that deny ownership such as housing organizations, co-ops, condo-boards. Building laws that that do not allow renting, owning pets and much more.
HOA Nightmares: After purchase, buyers may find that they are subject to harsh or unreasonable Homeowners Association rules and expensive fees that were not made clear upfront.
Is the property vacant, now and after sale, if the property is not vacant are the inhabitants paying rent and copy of the rental contract.
Various frauds, such as ensuring the seller is indeed the owner.
Tenants that refuse to pay rent and do not leave and the city won't remove them.
Bad Karma, in the entire US property market from tax sales, sheriff sales, foreclosures and so on. These people did not sell their full paid off "owned asset", it was stolen from them by the government and sold from under them. People did not leave on their own terms or on good terms and may have left unseen destruction on an unsuspecting new owner who is implicated in the bad karma generated by the government.
IMMORTALITY