Cash Money Sports is officially in business -- TMZ Sports has learned the agency has just signed its first high profile athlete ... Texas A&M wide receiver Mike Evans.

Evans -- considered one of the best players in the upcoming NFL Draft -- had initially hired another agency to rep him ... but we're told Evans has now signed on the dotted line with Cash Money.

FYI -- Cash Money is run by Bryan "Birdman" Williams and Ronald "Slim" Williams -- the brothers who built the Cash Money record empire ... the home of Drake, Lil Wayne, Nicki Minaj and Paris Hilton.

What's interesting ... Evans is tight with Johnny Manziel ... who happens to be BFFs with Cash Money rapper Drake.

So, the question ... will Johnny follow his wide receiver to Cash Money Sports?