AITA for not letting a plus sized person do some plumbing for my dad? I feel wrong about this decision.

I just wanted to use Chambers as a sounding board. I was given my dads old car when he bought my brother a new one, and I didn’t send the car in for maintenance for a year due to laziness. This past Monday I noticed that all the lights in the car go off when the headlights turn on, and I was advised to get my car checked out as soon as possible. I called a couple of mechanics and a few had a waiting list. My uncle knew a plus sized guy who does plumbing as a side job. I assume he’s good at it because he’s had a ton of work and had great reviews. I’m not sure why he would be so much cheaper and better than a regular mechanic, I’m just a student so I’m not too experienced with cars. I didn’t like the idea of giving a job to someone who isn’t a mechanic, but I could reschedule quickly and he was very cheap. <br><br>I called him and explained the issue so he told me he’d check it out and said he’d meet me at my place if I paid him upfront. I’m not sure why that was weird, I guess my uncle was vouching for him and said he was reliable so I went ahead and did it. He met me at the place, I handed him the keys, etc. He was about 420 pounds, and I’m not sure how he expected to get anything done. He had to walk a good fifteen minutes just to get to my car. He was panting very heavily, and personally I would never do any physically demanding job because of how hard it was to walk. I feel like I’m a jerk for this but I was worried that he’d have an heart attack or something while working. He hadn’t done anything yet, so I asked for my money back, and told him I didn’t want to risk his safety or anything like that. Without getting too into it, he called me a fat shamer and a jerk. I could have been more considerate with the way I worded it, but now I’m just really worried that he’ll be offended. It can’t be healthy to do that work, and I would have had a moral obligation to get him medical help if anything happened. I don’t see how I was wrong, but a part of me is telling me to just let him work and he’ll figure it out. AITA?