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The proof of accommodation for a Schengen visa application needs to be a document stating that you have reserved an accommodation for the length of the stay and that the reservation is confirmed:
Whether you are staying in a hostel, a rented room or a 5* hotel does not matter. Since you want to rent a house, you can rent it directly from the owner. At that point you should sign a rental contract stating the duration of the stay, the cost of the rental, the conditions, etc. This contract, signed by all parties, is a valid proof of accommodation.
As an added tip, I would suggest you sign an extra copy of the contract specifically for the embassy, to be included in your visa application.