Hiring a professional can be more expensive up front, but hiring someone who isn’t is usually more expensive over time.
This shed project was started by somebody who is not a professional contractor. They cut corners on materials to maximize their profits, while charging less than a pro service would.
They used a single joist and spaced out the boards on the deck to save themselves money. Those cut corners though will cost a customer more money over time. When the unsupported floor sags beneath the shed and causes the weight of the things inside it to crack the shed’s floor, the shed and the deck beneath will both have to be replaced. Basically - the customer will pay twice for their project! This is a bad investment.
When done correctly, the deck will properly support the shed and it will serve the homeowner for years, possibly long after they’ve left the home. That’s a smart investment.
Luckily this homeowner spotted what was happening early enough and switched to a real contractor.
Whenever you catch yourself debating whether to hire a professional contractor or a handyman, ask yourself “Do I want to pay for this once or twice?” You will find it’s always best to hire a professional.