AITA for not paying my landscaper when he didn’t finish the job

Months ago I met a guy at the local library. He was advertising his services as a yard worker and handyman. He seemed nice, so I took a flier with his contact info in case I needed help. My mom’s front landscape has become overrun by weeds this summer. She’s been trying to get rid of them, but they come back faster than she can eliminate them. I decided she needed help, so I called the nice guy from the flier. He came to the house to give an estimate. He said he should be able to have all the front landscaping done in six hours, including weed barrier laid down so we could mulch over it. This includes an island, and the part in front of the wrap-around porch. I told him he could focus on the island if that meant everything in the island got done: both the weeding and the weed barrier. He told me his rate for six hours was $210. I balked, because I make $12 an hour and this is a favor to my mom. But I decided I’d dip into savings to get it done. He came over a couple days and worked a few hours at a time. As I was leaving on the first day, I saw him on his knees with a shovel turning up the soil completely. I supposed that was a very thorough way to weed and thought to myself, “there’s no way my mom or I could ever do that. It’d be too hard on our backs and legs.” At the end of the six hours he worked, he’d only gotten maybe 2/3 of the island weeded, and no weed barrier laid. My mom was mad, feeling like he hadn’t kept up his end of the deal. I asked him why it wasn’t done and he said it just took longer than expected. Understandable: I, too, struggle with estimating how long something takes. You can see in the texts that I asked for a guarantee that the job would be done with the next $100. He assured me he could get it all weeded and the weed barrier laid down in three hours for another $100. He worked the three hours, and I saw him in the yard working hard and fast when I left for work. But he texted me later that the three hours is up and he’s leaving now. The job still isn’t done. I wouldn’t have rehired him for another $100 if I’d known the job wouldn’t get done — I would’ve hired someone else, or we would’ve pulled ourself up by our bootstraps and done the last of it ourselves. What do I do? AITA if I don’t pay him? AITA if I tell him “I’ll pay you when the job is finished?”