"No good deed goes unpunished"
I've wrenched in shops for 30+ years and...sigh...the vast majority of bikes I've had the "pleasure" or servicing have been dept store bikes.
I also was the person everyone in the neighborhood went to when their bikes needed repair. I always fixed the kids bikes...made sure they were safe and rideable, but when it came to lazy ass adults that wanted me to fix the pos bikes for free I drew the line. Upon realizing I was being taken advantage of I always state I charge $50 per hour plus parts, paid in advance in cash before I'd touch their bike. This quickly got rid of the "users" that just wanted something for nothing. Those that agreed got great service and I rarely charged for labor, usually just a few bucks depending on the condition of the bike and the quality of the person. A holes paid through the nose. If someone complained I never touch their bike again no matter how much they offered to pay.
While I pissed off some people, those that take advantage of others...good riddance...I also made some quality friends and acquaintances that are worth their weight in gold.