Short answer: Mortgage acts like overdraft. Pay in, take out. Income reduces balance daily. Requires discipline.
Your mortgage becomes like a giant overdraft. You can pay money in and take it out up to your limit. All your income goes into the account, reducing the balance daily. You pay less interest. But discipline is essential. If you keep withdrawing, you never pay it off. It is a tool for disciplined savers, not spenders.
Limit: $400,000
Income: $5,000/month
Expenses: $3,500/month
Net Reduction: $1,500/month
Interest Saved: Calculated daily on lower balance