I terms networth as the only way to sustainability. Income from the full-time employment is not stable and guaranteed. One can be retrenched without the advance notice at any point of time. It will be prudent to exclude the active income from the computation. The passive income from the investment portfolio is considered as non-guaranteed and one will have to be flexible to adjust his/her expense in accordance to the passive income. One can also consider leveraging the full-time or part-time employment to supplement the expense. It is always good to create some buffer on the income in relation to the expense.
An example is as such. If one generates $3,000 from his/her active/passive income (monthly), one budget to spend about $2,500 per month. The buffer of $500 will go to some extent of catering for the emergency or unexpected expense. This will varies from individual to individual. The most important thing is to create the buffer, regardless of the involved amount.