Can I take care of a rat infestation myself?

Over the past few months, I can hear what sounds like massive rats crawing around in my walls at night. I can even hear the sqeak. There is a panel on the outside of my mobile home that has my hot water heater inside. I saw a lot of rat dropping in there so I put a big snap trap with some peanut butter inside with no luck. I don't have the money for a professional pest company. I was gonna move out of this place soon, and rent it out, but I need to get the rat problem taken care of first.

Can I take care of a rat infestation myself?
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