I would caution against the use of poison....simply because nothing smells worse than a dead rat decomposing in the void space between units.

Back home, we had a rat issue... the one we poisoned crawled up next the void space between floors to die. Fortunately, we were able to get to the body out, but the smell was :ugh:.

Based on that ordeal, I found that spring traps work well... if you place them correctly.

Most mice and rats have poor eyesight; they use their whiskers as curb feelers and run along the baseboards.

In an area you know they pass by often, set your traps perpendicular to the wall with the trip plate butted up against the baseboard.

Then, when the fat fucks go scurrying along the wall, they step on the trip plate and THWAP.