Enough to live on, and it should be identified as such. Money held back for rent, groceries, and emergencies cannot honestly be described as capital irrevocably committed to the enterprise. Set the household reserve first, then a contingency for cost overruns and slow early trading, and treat what remains as the investable amount.
Keep three pots of money and label them
Separate committed business capital, preparation expenses, and living costs into distinct accounts and distinct lines in the plan. Preparation expenses, legal advice, translations, licensing applications, government charges, are not the investment, and current official fees should be confirmed for whichever step applies at the time. Overlapping the pots creates a figure that looks larger than the founder's real commitment, and it is the first thing a careful reviewer will unpick.
Name the figure the founder will not go below. Before any spending begins, write down the amount of personal savings that will not be committed to the business under any circumstances, and treat it as unavailable rather than as a last resort. A startup absorbs more than planned, and the pressure to draw on reserves is strongest precisely when the enterprise is least able to repay them.
Hypothetical example: a founder opening a boat repair yard fixes a reserve covering a year of household costs, declines to touch it when an equipment order runs over, and funds the overrun by deferring a second hire instead — a decision that is also visible and explicable in the plan rather than hidden inside a revised figure.