You can actually build muscles without weights

[Frank1985]

Google Front lever and Iron cross exercise, for example. It takes years to do them. You have the L-sit for stomach also. Of course, weights are infinite in resistance, but if you`re just getting started, why not:

Front lever:


Back lever:


The Iron cross:


The L-sit for stomach:

 

[ImmortalMedicals]

Solid point. People underestimate how much room there is to grow with bodyweight. The front lever alone can take 6-18 months of consistent work to achieve, and the iron cross is even beyond that — it's a B-level gymnastics skill, meaning even elite gymnasts treat it seriously. The L-sit looks simple until you try holding it for 30 seconds with locked arms and depressed shoulders.

For beginners especially, starting with bodyweight teaches you how to actually control your body before loading it with external weight. Most guys jumping straight onto a bar have no idea how to produce tension or stabilise their joints. Calisthenics forces that foundation whether you like it or not.