Buy a terrier or ask to borrow one from a friend ,cats aren't much good against rats,, you can try sealing up entrances using wire mesh and concrete rats can chew through concrete ,the wire mesh is to cut them up if they try , or you move. Rat poison will probably kill them,but rats aren't stupid and some are immune so that will take time. Plus having rat poison/traps around the house isn't great if you have children or other pets. Rats bite as well especially when cornered. They can come up through a toilet, in fact I read a story a while back where a dude was using the toilet and a rat came up and bit him on the ass.,luckily it wasn't his balls.
It wouldn't be fair to put a cat against a rat. a good terrier would rip a rat apart.
Brehs getting paid minimum wage had to catch Master Splinter on some Ghost in the Darkness tip
