He was the brother of Amos Simon Cottle but did not receive his classical education; he was for two years at the school of Richard Henderson. Henderson advised him to become a bookseller, and Cottle set up in business in 1791. In 1794 he made, through Robert Lovell, the acquaintance of Coleridge and Southey, then in Bristol and preparing for emigration to America. Coleridge had been offered in London six guineas for the copyright of his poems, but Cottle offered thirty, and the same sum to Southey, also proposing to give the latter fifty guineas for his "Joan of Arc", and made arrangements for the lectures delivered on behalf of pantisocracy. He facilitated Coleridge's marriage by the promise of a guinea and a half for every hundred lines of poetry he might produce after the completion of the volume already contracted for. This eventually appeared in April 1796. "Joan of Arc" was published in the same year.