You must have a portion of your wealth in FIAT money. You had to move easily for paying live expense, fees, local taxes.
If you can just have this portion ready to be used and for the rest you use btc... this is the perfect setup.
Of course, its much better that people invest money only when they feel safe for storing in that way. Otherways yoy will not like the experience...
That portion of you decide to put have in fiat is called a backup fund, and back up funds are characterised in 3, the emergency funds, reserve funds and the float funds, these funds are essentially built to cover live expenses just as you called it earlier. Although there are certain things one should take care of first before thinking about leaving funds in Bitcoin, essential expenses should be covered first, like food and other essential expenses,then after taking care of those expenses, you can put aside a percentage of your income for backup and whatever that's left could be used to purchase Bitcoin, that way you'll have cushion to protect your Bitcoin investment whenever future emergencies or expenses arise.