It depends a lot on the plane used for training.

To answer the question, I taught myself on a kit built 1/2A Ace Little Whizard with a Cox .049 with only rudder and elevator control. Only took about 3 flights at a park BUT I had extensive experience with years of control line flying and several thousand hours of full scale experience.

But as to the implied question of how long should it take to learn to fly, that depends on many things but I think the choice of aircraft is most important.

Some planes are very stable and will almost fly by themselves with minimal input from the pilot. Other less stable airplanes, make great aerobatic trainers but poor basic trainers requiring constant input from the pilot. Yet some folks prefer less stable planes for basic training because they think they can just learn it all with the same plane. Learning on the wrong plane is more difficult and will take longer.

Another often overlooked factor is durability. Most basic trainers are overbuilt and can easily withstand a minor mishap without damage. so the training that day can continue. Other trainers look cool or might be more aerobatic but are more fragile so a minor mishap ends the training session.

With the right trainer I can usually get someone to solo within 5 to 10 flights. Previous experience with a simulator, control line or free flight modeling or full scale flying will reduce that by 1/2. However, with the wrong aircraft used for training some folks give up and NEVER learn to fly.

Buy the right trainer, learn to fly in an afternoon and enjoy the hobby from that point forward OR buy the wrong plane and struggle for weeks.

My most successful trainer was a Balsa USA Stick Trainer, this is a stock photo (not my actual plane). Is it ugly? Heck yea! Is it durable? Double Heck yea! A plywood box screwed to a pair of hardwood rails is as simple as it gets, but it is an awesome flying trainer that can take a real beating and it’s really simple! I used to build them with 3 channels, no ailerons. I would buy the kit and build it in a weekend. All up cost with radio, plane, engine and covering was $200.

I taught many friends to fly usually in one afternoon and only a few flights.