by far the biggest cost in these things matty is the time needed to do the job, materials aren't the biggest cost.
as chris said, if you can do a lot of the work yourself then it will be far cheaper and much more rewarding to ride around in a car you resurected from the dead yourself.
welding isn't the hardest thing to learn, finding the best way to tackle the rot comes with experience but there's no better way to do it than for yourself.
think of it this way. you would be able to do the work for a couple hundred in materials, plus the cost of a welder.
good point with that though is when you've done that then you can take on paying jobs yourself to get the cash back
to be honest matty this is where a lot of projects fall down, when the owners have to pay to get things done. a grand doesn't buy you a lot of work nowadays on these jobs when you consider how many hours it will take to do a half decent job, plus materials, plus him making a living from it...