Wife fell in love with 5th wheel...I have an F150

My husband thinks from what he has read that we don't need a dually to pull a 40 ft 5th wheel. He says an f350 should do the job. We will want to be able to tow at least 18000 lbs. everyone has a different opinion, so who do we listen too? What happens if we don't get a dually. Keep in mind this is our first big truck and 5th wheel as we are new to this.