You would need to consult the rule book for your country's Amateur dancesport governing body. If you are in the United States, there are actually TWO bodies, USABDA (United States Amateur Ballroom Dance Association) and the NDCA (National Dance Council of America).

USABDA's rule book lives at
http://usabda.org/dancesport_competitors/rules-policies-bylaws/dancesport_rulebook/index.cfm

The NDCA's rule book lives at:
http://www.ndca.org/info.cfm?showsection=info&showsubsection=rules

The short answer, for dancers in the US, being paid for ANYTHING affects your status UNLESS you are officially designated an "Elite Competitor" under the USABDA system or a "World Competitor" under the NDCA system. To get these designations you need to place at a certain level or higher in certain events at the national championships.