I am also 17. But i too went time of service but had some incidents with clients saying they paid when they missed a week or two making me lose $$$$. only happened once or twice but other than that my size of business roughly 15 neighborhood houses was the best way for me to go.
That's why I never take cash, check's are numbered and put in QB's by check # that way I always have a record of all payments, no BS'ing me with I think I already paid crap! SYSTEMS SYSTEMS SYSTEMS guys you gotta have systems in place it's for your own good.