i'm a plumber, been freelancing in istanbul for 15 years. i used to do the work and buy/sell the materials myself. so if a customer said 'i want it piped', i'd get the pipes and keep a 30% margin in my pocket. like, i'd charge the customer 1300 TL for pipes that cost 1000 TL.
2 years ago my supplier (pipes, bolts, etc.) told me 'bro, quit this, i'll handle sales, you be the worker. focus on the job'. i said 'ok', it was super busy. the supplier was selling the goods right, i was doing the work. 3 months later i realized: i was losing 50k a month (300 TL loss per month, so 3600 TL a year). but the upside: i couldn't work 8 hours, i was working 12 (for shopping). now i work 8 hours, 4 hours free. no hassle at all.
i lost 50k but gained 'time freedom'. now i can invest in plumbing work, even started a sales side branch called 'store-ification'. i'm sure i'll earn 60k this year, i've already compensated for the 50k loss on the supplier's goods.