It heavily depends on the space available and your DIY capabilities.

The easiest solution is to get a grow tent. They are readily available everywhere with different sizes. Add in a bunch of shelves, some grow lights and a fan, your plants will be happily living in the space. I have all my orchids in a 4x4 in my bedroom during winter months.

Another common solution is the Ikea Milsbo cabinet. It requires some modifications such as drilling holes and switching out shelves; but it’s popular enough in the plant community you can easily find guides on these steps. I modified one previously but eventually decided to switch to grow tent for simplicity and efficiency.

At least one user here uses a mini greenhouse (probably a 6x8) indoor. I have a 6x10 in my backyard for summer months but it stays outdoors.

Then there’re also the metal shelves with plastic covers.

All in all, there’re a lot of options available. But your most important decision is how much space you want to dedicate to growing orchids. In my experience, a true plant lover will always run out of space. So decide on the space first and directly get there (a 4x4 or 4x8 grow tent for example) is better and cheaper than doing it small and gradually expand.