Hi–even a pricier uke can be junky–high action, no resonant tone, especially if made of plastic or very thin body – see past the pretty decorations and spend some time at a local music shop (they’ve already screened for quality). Don’t buy the entry level $40 uke unless budget is absolute top priority and your learner is very young, likely to disrespect and forget a real instrument. If you can, spend a bit more – $80 to $100 gets something pretty good for a beginner, and an instrument that won’t get frustrating or have to be replaced as soon as the student has some skills. Start with a concert uke (bigger), not the smaller soprano uke for children 8 & up. The tiny ukes soon become difficult for growing boys to play, for sure.
There are now SO many ukes on Amazon, I can’t recommend one anymore as I used to; I don’t know all the brands. What I really recommend is going to a local music store to listen to a few and get the opinions of the experts. Ignore the decorations and focus on the tone quality: remember, you can decorate your own uke with paint, markers, stickers as you want without damaging the music quality. Even if you’re spending $10-$20 more, it is truly well spent money. The instrument won’t be garbage like some of the ones turning up in my classes, and it will already be pretuned.
I say the same for guitars: if an instrument is too poorly made to play easily (high action, no resonant tone, hard to tune, won’t keep tune, ugly tone), then no child will want to play it. An instrument is not a toy; don’t buy a Toys R Us guitar. Go to a music store and get an entry level guitar of a good brand: Yamaha makes an excellent entry level 3/4 or 1/2 size guitar for smaller hands. Fender’s entry level acoustic is also of excellent quality. It is an instrument you won’t have to replace later.
Here’s a buying guide with some basic ideas to think about: https://www.beginnerukuleles.com/how-to-buy-a-ukulele-buying-guide/