Expect Google Maps visibility to move within a few weeks of fixing your Google Business Profile, website rankings to build over three to six months, and steady organic enquiries in six to twelve months. Competitive services in inner Melbourne suburbs usually sit at the slower end of that range.
The early gains come from things Google reads straight away: correct categories, a complete profile, real photos and new reviews. The slower gains come from service and suburb pages and links, which take time to build and for Google to trust.
If you need enquiries sooner, run Google Ads while SEO builds, then shift budget as organic enquiries grow.
This is one part of a bigger picture. How to choose an SEO agency in Melbourne covers costs, contracts, what good SEO includes and how to spot a bad agency in one place.