I've seen lots worse than this that people have been able to get back to good, working condition. I would suggest you start with the thread, which is second from the top of this forum page:
How to Clean Up and use a vintage sewing machine - videos by Muv and Fav
I would start with metal polish on the machine. Sometimes, it will take off the rust if it's not too deep. It's easier to use and less caustic than some rust removers. I don't know what brand I bought, but I got it at the grocery store.
Your machine looks like a model 15 to me. I'm no expert, but when the tension is on the end, it's usually a model 15.
After you watch some of those videos that Miriam suggests, you'll have a sense of direction on where to go from here. Most everyone on QB will be happy to help in any way they can. We all love old sewing machines.
bkay