Azad Miah, 44, was also found guilty of running a brothel from his business and paying two teenagers for sex.
Miah was owner of the former 'Spice of India' restaurant.
Judge Peter Hughes said the case at Carlisle Crown Court showed "the seedier side" of UK towns and called for more protection for children.
Miah was cleared of child prostitution allegations relating to two other girls, the BBC reported.
Hughes said the conduct of the married father of four "corrodes the foundations of decency and respect by which all right-thinking people live their lives."
Detective Inspector Geoff Huddlestone of Cumbria Police, said Miah had got the sentence he deserved and that he had "committed heinous crimes".
The hearing heard that one girl was encouraged to have sex with him out of desperation for cash when she was 15, while he had a sexual relationship with the other, a heroin addict, when she was aged between 15 and 17.
The jury also heard that the Bangladeshi national had targeted "desperate and vulnerable" victims and treated them in a "cold and clinical way," Judge Hughes said.