Keeping the sources of food and other things that rats seek out at a minimum is likely to go the furthest comrade. I’m not in pest control but going straight for the poison route makes me think it is just as likely to make someone there sick by accidental exposure.
Also, depending upon the type of rat (Norway rats for example), it can be resistant to warfarin and other types of poisons available for those without a pest control license. At that point you are likely wasting money, exposing humans to poisons unlikely to affects rats, etc. And supposing you get hold of the newer types of poison, and someone ingests it accidentally or otherwise, some of the newer poisons aren’t “fixable” like warfarin exposure in humans is.