To qualify for the first home owners grant you must live in the property for at least 6 months. You don't have to move in immediately but you have to move in with 12 months of purchase.
The type of loan doesn't affect eligibility for the grant.
A lot of young people purchase a property, with the intention of turning into an investment property after meeting the grants criteria.
If you buy a property as an investment and later decide to move in, you can apply for the grant at that time. You'd apply for the grant separately from the bank.