It depends on your background, but with 6 hours a day, you could gain a solid foundation in 6-12 months. Start with Solidity for smart contracts (popular in Ethereum) and learn Rust if you're interested in Solana or Polkadot. Job opportunities are growing, but focus on building projects to showcase your skills
It would even take more for a person without the background coming from humanities.
And if the person has a 9 -5, there is no way to study for 6 hours a day. It is going to be less and it will take up to 24 months to master the basics.
And it is going to be hard, when there is no experience. And when you have reached a point where you feel competent, the next obstacle is finding a job. With a good portfolio, it will take a while because it is a saturated job market. Positions are very competitive.