You need to go into this with your eyes wide open, secure financial resources if you are paying others to do the work, competent skills if you are not and plenty of time on your hands. Clearly it depends what kind of finished result you are aiming for in terms of quality and authenticity.
Early 911s rot in lots of places. The list is usually as follows: front fuel tank support, front slam panel, outer sills, intermediate sills, "A"post supports, "B" supports (so called kidney bowls), rear seat pan, rear parcel shelf, around the rear torsion bar tubes, inner wings, floor pan, all outer panels including doors. If a sun roof car: the roof around the sunroof and windscreen A post area as the sunroof drain tubes get blocked. These are just the usual areas and there are other surprises in store. So called "dry state" cars are often just as badly corroded. You need to get someone who knows what they are looking for to check the car over. Even then lots of rot can remain hidden from view. As can be seen I have not even mentioned suspension components or engine and gear box. A "cheap" engine build is anything between £8k and £15K. Parts prices for early Porsche cars are very steep indeed and there are many parts that have not been reproduced so you need to find used ones.
I am on my second early 911 project and I would suggest you visit DDK and look at the restorations on there. There are also plenty of discussions about the cost of a full restoration where even doing a lot of the leg work yourself can come in at £60k and no that is not a typo or an exaggeration. Tread very carefully.
Regards
Kirk