The short version
Use the pets you already own to establish a current income rate, collect what the game gives you while away, and reinvest only the amount that leaves your chosen base-defense reserve intact. A raid can add a pet, but it can also expose your own base, so it should not be treated as free farming.
Money farming is not a separate clicker route: pets are the income source, the roll target, and the asset another player may steal. That means the fastest-looking cash decision can weaken future income if it drains the reserve or encourages an exposed raid. Sustainable growth matters more than one large number.