You can download the electronic version of the second-hand house online contract by following the following steps:

1. Log in to the house registration system on the Internet and enter the online contract download page.

2. Click on the electronic contract to be downloaded to enter the electronic contract details page.

3. Select the electronic contract to be downloaded and click the "Export" button to download the electronic contract locally.

4. Click to download the completed electronic contract and select the printer to print.

It should be noted that the specific operation interface and steps may vary depending on the region and system, but generally speaking, the above steps can be used as a reference. If you encounter any problems, it is recommended to contact the relevant department or technical support personnel for consultation.