ADDED: There is a common misperception that if you live together for a certain length of time (seven years is what many people believe), you are common-law married. This is not true anywhere in the United States.
See below link for further information:
The SC adultery laws are quoted below:
SECTION 16-15-60. Adultery or fornication.
Any man or woman who shall be guilty of the crime of adultery or fornication shall be liable to indictment and, on conviction, shall be severally punished by a fine of not less than one hundred dollars nor more than five hundred dollars or imprisonment for not less than six months nor more than one year or by both fine and imprisonment, at the discretion of the court.
SECTION 16-15-70. “Adultery” defined.
“Adultery” is the living together and carnal intercourse with each other or habitual carnal intercourse with each other without living together of a man and woman when either is lawfully married to some other person.
SECTION 16-15-80. “Fornication” defined.
“Fornication” is the living together and carnal intercourse with each other or habitual carnal intercourse with each other without living together of a man and woman, both being unmarried.
Whether or not these, somewhat antiquated, laws would actually be charged or not, is an unknown factor.