I think the hardest thing anyone entering this hobby has to learn is to identify what is a bargain and what isn't.
The first thing to consider is not how much a restoration will cost, but how much of your money it will cost. It is always better to buy a project car that someone else has dumped thousands into, then lost the will, spouse approval, or finances to complete; than to be that guy yourself. Next to the sound of a 440, there's no sweeter sound to hear than "my wife says it's got to go!"
When it comes to these types of cars, their price progress on a non-linear scale based on how much work has been done to them. For example, start with a POS project car that someone bought for $3,000, and dropped $5,000 into. Most of these guys know they won't see $8,000 for the car, and will end up selling it for about $5,000 or less just to get out from under it. So you pay $2,000 or less more for the upfront price, but you're getting $3,000+ in restoration that you don't have to pay for. That's a real bargain.
If you've got money to put into restoring a car, you've got money to put in a stash account to buy a project car that's further along the restoration process. I would take that 71 Roadrunner with major rust issues, sell it, put that money into an account and add the money you would have dumped into it to the account. It won't be long before you've got enough to afford a car that needs a lot less work.