To set up a secure SSH server for your home computer to make it accessible anywhere AND to use it as a port forwarding proxy.
WinSSHD version 5 is free for personal use. So download and install it. You can download it from the link http://www.bitvise.com/download-area
Create a new user with a very complex (containing characters from multiple sets like uppercase, lowercase, special characters, numbers..) password. Assign permissions very carefully to this user. Give full access only to one sandbox folder and as required, give read access to the other folders.
Download WinSSHD Tunnelier (or some such SSH2 Client) and generate a client certificate key pair (public+private). This would be the second level authentication for your server.
In WinSSHD control panel, remove the Virtual Groups and Virtual Users (since we'll use the Windows authentication instead).
Add your new Windows User to the Windows Users section and ensure you have chosen "Required" for password AND public key authentication.
Assign the public key generated in step 3 to the user.
Click OK to confirm your selection and apply the changes to the WinSSHD Server.
Open port 22 in your firewall and your router (if you have blocked port accesses). Haven't configured it yet? Do so immediately :-).
Use a SSH2 client to test the connection to ensure both levels of authentication are REQUIRED and you are not able to access without both your password and your private key.
You're done. You must now be able to access your Home PC over SSH2 (which includes, SFTP, command prompt access, remote desktop access, port forwarding, etc.). If you don't want to do so many things over the internet, use the WinSSHD Control Panel to turn-off all the services that you don't require.
for details on securing your WinSSHD Server.