The cost of hiring a Google Ads specialist depends on the experience of the specialist.
An experienced Google Ads expert can charge anywhere from $15 per hour to $100 per hour.
It depends on the hiring setup.
If you are a local service provider and spend around $3000-15000 per month on Google Ads, you should hire a Google Ads specialist on a monthly retainer.
With that, you should set up some targets for the number of leads and cost per lead. Once you work with this person for some time and see the conversion data regularly, you would know how to improvise and scale further.