You can start your Camino at any point of any route. In order to get a Compostela certificate, at minimum you need to walk from Sarria. Since taking a 5-6 week sabbatical or a vacation might be challenging, quite a few people stretch their Caminos over few years in 1-2 week stages. Some Europeans walked from home to Santiago … just like in the old days
- Getting there
St. Jean Pied de Port is a popular starting point. The closest airport is Biaritz, and a train will take you to St. Jean. Alternatively you can get there from Spain from Pamplona, Bilbao and Barcelona are closest airports with low cost flights. If you are starting from Leon the Asturias-Oviedo airport has good low cost connections.
On the average the daily cost is 20-25 EUR per day. There is a nice interactive calculator for detailed overview.
Cash is preferred mode of payment , in smaller villages cards are very rarely accepted. My advice is to carry a couple of hundred euros and re-stock at ATM’s in major cities along the route.