Seller assuming the mortgage
It's possible for the seller to finance the purchase in part or entirely, depending on what is negotiated. This is a private arrangement between buyer and seller that sometimes occurred because foreigners historically had great difficulty in obtaining a mortgage.
The owner sells the house to the buyer, but only receives a certain percentage of the amount. The rest will be paid on a monthly basis plus interest. The exact terms are all open to negotiation. Until the money has been completely paid the land title will still be in the original owner's name.
If both parties agree on this course of action, the purchaser must be absolutely certain that the seller is indeed the owner and has legal authority to sell the home or lease the land. A title search will list the legal owner(s) of the property. Make sure that all documents and agreements are notarised.