Your travel authorization has been approved and you are authorized to
travel to the United States under the Visa Waiver Program.
So I’ve been accepted onto the Visa Waiver Program/ESTA. I’ve been to America before on a separate ESTA in 2015 with no problems. But this time I plan to take a trip into Canada for a few days with my America friend in his car while I’m over in America.
Flying in and out of JFK on both ends of my overall trip, trip is 3 weeks long overall, just wondering will I have to get another visa to enter Canada? Will I have to pay a fee for reentry to USA, or get another visa to enter back into the USA?
No, you shouldn’t have an issue (barring the usually caveats about eligibility for entry into Canada etc).
The ESTA is just required for you to fly to the US – you enter under the Visa Waiver Program, which will give you 90 days (or shorter if the Customs and Border Protection officer deems it necessary to limit your trip – you can mitigate this by explaining your plans to him).
You do not need an ESTA or an ETA (Canadian version of the ESTA) to travel to Canada via ground or sea, it’s for entry via air only.
As a British citizen, you enjoy the ability to request a visa at the Canadian border, which you shouldn’t have an issue with unless you have outstanding issues with Canadian immigration or police.
You don’t have to pay a fee at either border, and so long as you stay under 90 days total (or whatever shorter limit the CBP officer sticks you with) between the two countries you should be let back into the US without any concerns at all.