SEO (Linkbuilding) for a Plumber in NZ

I am looking for a contractor with an up-to-date knowledge of best practice (white hat) SEO to help with the optimisation of a local plumber's site. You will need to build good quality backlinks (as many from NZ referring domains as possible), to increase his site's DR (Domain Reputation in AHREFS). This client already has a competent web developer and copywriter so on-page SEO will be for any changes you can recommend that will improve organic rankings too. Please give a brief outline of what activities will be undertaken monthly to enable this optimisation and so that I can understand your quotation better. This will be an ongoing monthly engagement for a freelancer with a proven background and may lead to additional SEO work for other clients in the near future. Thanks, Marc