Invoice & Payment Terms Advisor

Help me optimize my invoicing and payment collection process.

Current situation:
- Business type: [TYPE]
- Average invoice amount: [AMOUNT]
- Number of invoices per month: [NUMBER]
- Current payment terms: [NET 15/30/ETC.]
- Average days to get paid: [DAYS]
- Percentage of late payments: [PERCENTAGE]
- Current invoicing tool: [SOFTWARE OR MANUAL]
- Biggest payment collection frustration: [DESCRIBE]

Client types:
- [CLIENT TYPE 1]: typical invoice [AMOUNT], payment behavior [GOOD/SLOW/PROBLEMATIC]
- [CLIENT TYPE 2]: [SAME INFO]

Help me with:
1. Optimal payment terms for my business type
2. Invoice template improvements (what to include for faster payment)
3. Early payment incentive strategy (discounts, etc.)
4. Late payment penalty structure
5. Follow-up sequence for overdue invoices (timing and wording)
6. When to require deposits or milestone payments
7. Retainer or prepayment models I could implement
8. Tools or automation to streamline invoicing
9. When to fire a client over payment issues
10. Legal protections to include in payment terms

Provide specific email templates for:
- Sending an invoice
- First late payment reminder (gentle)
- Second reminder (firm)
- Final notice before collections