That depends first on the car, what kind of condition it is in, and then on your intended purpose. A show car is going to be a lot more expensive than a cruiser, naturally.
I shop Mustang Parts stores online for pricing. For example,
www.laurelmountainmustang.com sells interior trim and other items in kits that save a lot of money. My 65 Pony interior was $850 complete with the kit and the seat foam. Separately, it would cost at least $1000. They sell light kits, weatherstrip kits, and other things like that, the complete package, everything you need.
Paint is expensive, whether you do it yourself or have it done. If you do most of your own work it saves money. But you need to make sure your work is good, because if your body work is not good, the paint will not be either. I always strip to bare metal, you know what you are dealing with, good or bad, and you don't end up with waves down the side from sanding.
You also need a place to work on it. My garage is adequate, but I would KILL for a shop, because I have to quit early enough to clean up so I can put my Vert back in the other side. Tools are good to have, I have acquired more tools than Tim "the tool man" Taylor. The right tools make the job go better. Don't get in a hurry, but don't bog down like me, my 65 has been sitting while I have been doing other things, and it's hard to get back to it.
If you need advice, want ideas, my email is
haroldbob@hotmail.com, be sure to put Mustang somewhere in the Subject line, because everything coming from an address not in my address book goes to junk mail, and I may delete it if I don't know it is real.
I have been a Mustang junkie all my life, grew up 4 blocks behind the local Junior College and walked home from Elementary School back in the 60's when the parking lot was full of Mustangs. I have been restoring old Mustangs since the 80's, and got into the newer Mustangs in 98 when we bought my Vert. I have lots of sources for parts because I read Mustang Monthly and Mustang and Fords both cover to cover. I also write the newsletter for our local Mustang Club, so I usually know about used parts available, although they are local.
Don't feel like a pest, I love to see people get into the hobby, especially younger people, it keeps the hobby alive and active, brings new blood into the arena and keeps it fresh. Good Luck with your 67 Fastback, I want to know how it comes out!