How practical is the flat transformation done in the movie 'Wake up Sid' ?

https://preview.redd.it/cwahua6hhqje1.png?width=925&format=png&auto=webp&s=262981545a5a9fcdca97d5723f235fbdc16c7c3f Is it a good idea to rent an unfurnished, unkempt flat and furnish it over time? Many people move out after a year or two, so is it worth investing in new or second-hand furniture and décor, especially when sharing expenses with a flatmate? How do you typically handle furnishing and moving when relocating to a new place? Also, do landlords generally allow tenants to paint the walls?