Is doing a Habilitation a financially viable decision?

You have to distinguish things here:

1. A Habilitation is a qualification level (not quite like an academic degree but you can think that it is sort of a grand PhD with additional teaching). This does not mean that you have to be employed but in most cases you will be because otherwise it is going to be a bit difficult to finance your life for the time it takes (normally 4-8 years)
2. A Habilitation used to be the formal qualification level to become Associate Professor and Full Professor. The position of an Assistant Professor (German "Universitätsassistent") was usually the time when you worked on obtaining the Habilitation. Today most job advertisements do not ask for a Habiliation anymore. Instead it states something like "Habilitation or equivalent qualification". This allows hiring of international professors.
3. In daily university life a Habilitation might still be of significant advantage. You (sadly) still hear phrases like "This guys does not even have a Habilitation - what does he even want". Also nobody will questions your ability to supervise students if you have the Habilitation (you can also without but it definitly still helps)
4. In non-academic jobs as in industry you will certainly not need a Habilitation. It might rather be a disadvantage as you will be seen as overqualified.