In an attempt to start my career as a film director with an ambitious short film, I produced it with my own money, and here's what I learnt:
1. Start the financial process at least six months in advance.
2. There's always stuff you're going to miss in the budget, so add a safe margin.
3. Go high in the budget and then lower the costs. Not the other way round.
4. Set realistic rates for a shortfilm, like 50% of a regular TVC rate, for each member of the crew, and not, a round rate for all. There's a hierarchy for good reason. Negotiate with your crew about their 50% rate to avoid misunderstandings.
5. Always write down in an email the agreed rate, conditions and budget with each person or department prior to start work.
6. It's nice to go legal, but unless there's a production company behind it, go black. Nobody cares for a 3 day social security anyway.
7. Paying a simple insurance however is worth it.
8. As for conditions to agree with crew, take into consideration: If social security, rate goes lower. If black, no liabilities attached. If catering, no extra coffees to pay for. Extra hours!
9. Find a production manager who has experience in finding low cost stuff and brief them very well with the budget.
10. Share the budget and stick to the budget!
11. A production assistant in time is better than becoming an overloaded director.
12. Don't hire a portable WC in a short film....absurd luxury.