Is it illegal to serve defendants the forms of a civil case as requested by the plaintiff who i just met?

;ets say if i dont know the plaintiff and i offer as a favor to serve the defendant or someone being sued the small claims papers that they must attend to the court date? im 18 and i would not mind serving people since i konw there's those people who charge to do so or even the sheriffs charge too. i understand if the person i am serving is not there i have to keep trying until they are aware they are being served to appear to the court date.