I really don't think job security is paramount here in things to consider before investing into Bitcoin, because in life anything can happen, even the job you feel that is secure, they might just lay you off for no just reason, because life is unpredictable, and that is more of the reason why we should not play with our savings and emergency fund, because that is what going to keep you going till you get another job.
A job is definitely needed to keep bitcoin investment right, if you are out of a job then you can decide to sell your bitcoin holdings if you face any danger. So this is why the job is special, you can keep your investment active in the Bitcoin DCA method with a portion of the income from the job. There must be an external source of income to meet basic human needs. Bitcoin holdings would not be sustainable for long without eros.