Over the last 10 years I have owned one 18 ft trailer and 4 different tow vehicles. Living out west where strong head winds, high base elevations and steep mountain passes all rob a tow vehicle of it’s power I would suggest at a minimum a tow vehicle rated to pull at least twice the max weight of your trailer and three times would not be going overboard.
As a beginner joining “Good Sam” and reading their magazine will help you avoid a few mistakes!