Today, the Secret Service is authorized by law to protect:
the President, the Vice President, (or other individuals next in order of succession to the Office of the President), the President-elect and Vice President-elect; the immediate families of the above individuals; former Presidents, their spouses for their lifetimes, except when the spouse re-marries. In 1997, Congressional legislation became effective limiting Secret Service protection to former Presidents for a period of not more than 10 years from the date the former President leaves office.
children of former presidents until age 16;
visiting heads of foreign states or governments and their spouses traveling with them, other distinguished foreign visitors to the United States, and official representatives of the United States performing special missions abroad;
major Presidential and Vice Presidential candidates, and their spouses within 120 days of a general Presidential election.
I am not exactly sure of this but I believe the Secret Service requires a President/Candidate to designate one residence as a primary and they protect that one exclusively. The others get incidental protection if used from time to time.
I am not aware of any requirements for the Secret Service to "pay" an ex-President's bills. Savings and a pension plan take care of this.
God bless our troops wherever they may be.
Surely that just means 120 days BEFORE an election, not also continuing 120 days AFTER???