A variety of prefixes and words that express former and future states of being are available to writers. Here’s a discussion of the possibilities.
In reference to people who are no longer in a particular position or profession, the most common wording, for example, is “former stockbroker John Smith” or “ex-stockbroker John Smith.” Other, more elaborate terms, in ascending order of ornateness, include onetime, erstwhile, and quondam.
One can also use once or “at one time,” but not as a simple description preceding the name, as in the examples above; one would have to write, depending on context, something like “John Smith, once a stockbroker himself” or “John Smith, who at one time was a stockbroker.”
Descriptions might also use then as an adjective, as in “then stockbroker John Smith” (note that the phrase consisting of then and a descriptive word is not hyphenated), which is distinct in meaning from phrases that include former or ex-: For example, “The book was written by former stockbroker John Smith” means that Smith wrote the book after he was no longer a stockbroker, whereas “The book was written by then stockbroker John Smith” means that Smith wrote the book while he was a stockbroker but is no longer working in that profession.
A more complex form is to use turned as a transitional term between a former state and a current one, as in “stockbroker turned mechanic John Smith.” (Note that hyphens are not used to connect the terms; that common error likely arises from confusion with phrases that include the term cum — from the Latin word for “and” and therefore not synonymous with turned — which appears in such constructions as “teacher-cum-coach John Smith.”)
Unfortunately, this variety of solutions is not available for expressing future states. Future is the only simple description, as in “future stockbroker John Smith.” Otherwise, one might write, “John Smith, who will become a stockbroker” or, in retrospect, “John Smith, who went on to become a stockbroker.” (However, politicians who will take office on a specified date can be referred to as, for example, “President-elect John Smith.”)
The effect on a job title of the insertion of former, ex-, or any other similar term (or any adjective, for that matter) before the title varies according to style. The Chicago Manual of Style and similar handbooks generally treat the job title as if has joined the adjective as part of an epithet, a generic description rather than a capitalized title. Therefore, someone who no longer holds a particular office would be described, for example, as “former president Bill Clinton,” as opposed to the designation “President Bill Clinton” for a sitting president. The Associated Press Stylebook, by contrast, does not make this distinction: The form most newspapers follow is “former President Bill Clinton.”