[hazard]

I was in a similar 'unpredictable income' situation when I had my kid. Since you're on HN, I'm assuming that your income comes from some kind of knowledge work, and you have to be mentally sharp to be productive.

The best investment I ever made was to get a night nanny. This is someone who comes to your home at night and changes diapers, feeds the baby (or brings them to the mom to nurse without waking you up) and may also do basic domestic stuff like laundry and dishes while your partner adjusts to their new routine as a parent.

The cost is going to vary dramatically depending on where you live and whether your kid has any kind of special needs (e.g., if they're a premie you might want a night nanny who is also a registered nurse).

They will basically double your productivity during your waking hours since you will not be suffering (as much) from sleep deprivation.