A number of caveats are in order here. First off, being in the early twenties would be atypical for a Luftwaffe recruit during the Second World War as the Third Reich instituted conscription at age 18. Conscripts had no choice in their branch of service, but one could voluntarily enlist before their eighteenth birthday or for a longer duration of service. Although such individuals had no guarantee of which service they could enter, there was some choice. This is the path a number of Luftwaffe pilots took. Second, a popular component of the Reichsarbeitsdienst (RAD), a six month period of compulsory labor before military service, was the Nationalsozialistische Fliegerkorps (NSFK) which provided glider training and certification for German youth. This was part of a broader program to develop air-mindedness among the German population along with Hitler Youth glider clubs. Many Luftwaffe pilots had this gliding experience and it gave them a leg up in being accepted into service. So many recruits would have had some knowledge of flying, especially in the early war period. Finally, the training periods varied quite widely throughout the war. The training schools began to cut corners as the war worsened, so a lot of what I will describe below became telescoped or jettisoned because of the war.
The first step in training was the Fliegerausbildungsregiment (FAR- early and prewar, there were known as Flieger-Ersatzabteilung), one of 26 training units which introduced the recruits to basic military discipline and rudimentary elements of aviation such as radio work. The FAR also weeded out those unsuitable for pilot training and channeled the washouts into aircrew or groundcrew service. The FARs were to last six months, but gradually shortened under pressure from the war. The pilot candidates would then enter into a Flug-Anwärterkompanie for basic flight training for about two months. The next step was the Flugzeugführerschule-A/B (F.Z.S–A/B) which were formal flight schools where the pilot candidates would accumulate light time on trainers. A-schools introduced pilots to rudimentary elements of flight and eventually solo flights. The B-school introduced pilots to more advanced aircraft, often now obsolete variants of frontline aircraft. The students would log around 100-150 hours of flight time over the course of several months in the F.Z.S–A/B, but again, wartime pressures whittled that down significantly. The pilots would then go to specialized training schools upon completing the F.Z.S–A/B, such as Jagdfliegerschule (fighter school) or Flugzeugführerschule-C for multi-engine or other advanced certifications. These training schools emphasized skills particular to each branch of the Luftwaffe such as dive bombing or fighter formations. The penultimate stage was operational training with frontline aircraft under the auspices of Ergänzungsstaffeln/gruppen of the various Geschwadern which could last anywhere from a couple of days to a few weeks. Frontline pilots would introduce the tyros to combat tactics and simulate the combat environment. As the war situation worsened (sensing a familiar theme here?) these transitional units were pressed into combat service or enfolded into the specialist training schools. From there, it was a posting to a combat unit.
So in short, a Luftwaffe recruit probably spent between eight months to a little over a year in training before being sent out to a combat mission in the early stages of the war. As the war situation worsened, pilot training was shortened considerably and the advanced components of the training establishment were pressed into combat service.
Sources
Fischer, Wolfgang, and John A. Weal. Luftwaffe fighter pilot: defending the Reich against the RAF and USAAF. London: Grub Street, 2010.
Hannig, Norbert, and John A. Weal. Luftwaffe Fighter Ace. London: Grub Street, 2004.
Ketley, Barry. Fledgling Eagles: Luftwaffe Training Aircraft 1933-1945. Hersham: Classic, 2009.
Stedman, Robert F., and Karl Kopinski. Jagdflieger: Luftwaffe Fighter Pilot 1939-45. Oxford: Osprey, 2008.
_. Kampfflieger: Bomber Crewman of the Luftwaffe, 1939-1945. Oxford: Osprey Publishing Ltd, 2012.