Deposit, equity and LMI
Most investors buy with either a cash deposit or equity from a property they already own. Equity is the difference between what your home is worth and what you owe on it, and lenders will usually let you borrow against part of it.
If you borrow more than 80% of the property's value, most lenders charge Lenders Mortgage Insurance (LMI). Sometimes paying LMI makes sense so you can keep cash in reserve, and sometimes it does not. We can look at both options with real numbers.

