This will depend on the car and the hitch kit.
The Hitch I put on my Fiero to pull the rase tire trailer to events was a bolt on in two hours affair.
The one for my Kia is going to be a pain, the rear bumper cover is removed, the bolts to hold the metal bumper to the car are removed, the tail pipe removed.
The hitch is bolted up and holes drilled for extra bolts, all the bolts are loosened off and the hitch allowed to hang, the bumper cover re-installed, the hitch bolts tightened and the new tail pipe hanger installed. Book says 3.5 hours, at home in the garage all day.
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