Google Ads can bring in the first enquiries within days of going live, because your ads show as soon as they are approved. Expect the first month to be a learning period while the agency cuts wasted searches and tests ads, with a steadier cost per lead from the second or third month.
Allow 60 to 90 days before judging an agency, as long as tracking was working from day one. That gives enough data to see which keywords, ads and suburbs produce work.
If you have had no enquiries at all after a few weeks of steady spend, ask to see the search terms report and the conversion tracking setup. One of them is usually the problem.
This is one part of a bigger picture. How to choose a Google Ads agency in Australia covers fees, ad spend, account ownership, proposals and timelines in one place.