My sister shouldn’t have let her boyfriend try to fix the furnace

My sister and her boyfriend have been together for the past 6 months. They moved into my sisters house together after two months. My sister brought the guy over to the house to meet our mom and dad. I was at the house as well. I did not get a very good vibe from the guy. He didn’t seem like that type of guy that my sister would normally date and I was immediately worried that she made a bad decision. Now I absolutely feel certain that my sister should get rid of that guy. Dwayne told my sister that she could fix the furnace in her house, so my sister decided to let Dwayne work on the problem instead of contacting a furnace repair technician. Dwayne told my sister that the furnace repair would be easy. My sister tried to call the repair company, but Dwayne insisted that she was only wasting money if she did not allow him to fix the problem. I’m not sure if Dwayne knew what he was actually doing or if he was just trying to save the day, but he ended up doing more harm than good. Dwayne could not fix the furnace and my sister had to call a furnace repair company to finish the repair. The total amount for the repair was almost $300 and Wayne refused to pay any of the cost. The guy lives in my sister’s house with her two kids, but he refused to help pay for the furnace repair. I absolutely feel like this guy is trying to use my sister.