The ebikeling kits on amazon have decent reviews. I've bought his ebay products, in fact, have at least three of them. All were the 500W geared motor. His LCD displays don't work right with geared motors. I had one kit with the LCD, and I replaced the controller/LCD with different models. I have no problem with the LED models, but they only have 3 PAS levels. The kits have a 22 amp controller and will push your bike around at 20-22 mph on 36V.
He sells a direct drive motor, which I've never seen. The nuances of DD motors, heavier weight, difficult to pedal w/o power, but simple with high speeds, don't attract me.
My two ebikeling 36V 500W kits. First one is an old Trek with the LED display and 3 level PAS. $200 kit and $280 36V10AH battery. Motor went on in 2015 and has never come off (no flat tires), Battery still useful. Second is a Schwinn my neighbor threw out last year. I had the LCD kit for $210, but I used a different controller/LCD ($75). Both are 20-22 mph.
I also built a mid drive with Bafang BBS02, I rode it in Colorado past the "no ebikes" signs back in 2017, with the highly visible rack battery covered with pannier bags and duct tape. That build was over $1000 back in 2016 when batteries and motors cost more than today. For a beater bike, go with a hub motor, but get a safe battery or build it safe.
