I would suggest making a list of everything you need to fix on the car.
Break each task into two catagories - parts and labor.
Research what parts are going to cost.
Labor can you perform the task.
Is it something you can do or learn.
Do you know how to weld.
Are you good enough to do structural welding. Remember your safety is at risk.
If not how much will that cost.
If you still think you can do it you need to determine if the rust has compromised the structure of the vehicle. Also when you total up all the costs how are you going to get the money and how long will it take.
I would recommend doing this for any project. A little planning will save you money and frustration.