You use SSH port tunnelling on a Windows Server to access MS SQL? I'd be surprised if that was "simple." But go ahead and explain it.

We do here where I work. We're running Bitvise SSH server on Server R2/2012 and you can use bitvise tunnelier or putty as the client(maybe others, just have used those two myself) and then connect via management studio once the SSH tunnel is connected. We also require both key and password auth. We also do RDP over the SSH connection as you can't remote to those machines directly.

I'm not sure if $200 in third party software counts as easy. In particular when you could be using RRAS instead, which is built in.

Bitvise server is $100, but now you want both simple and free? It's well worth the $100 IMO as it's pretty easy to setup and manage accounts and keys. You only said "simple" before, and I consider it pretty simple to get up and running. I didn't pay for it, but $100 one time is pretty negligible for what we use it for.

If they are using MS SQL, chances are SSH isn't even in their toolset.