Ukulele Recommendations:
To start with, you might borrow a ukulele. Ask around! Many people have a good ukulele lying around collecting dust and would be happy to lend it out as you start your ukulele journey. New ukuleles are also quite affordable (about $40 and up), but please be wary of very cheap ukuleles. They often have fretboards that are incorrectly calibrated so that chords play out of tune and strings that are set too high, making it painful to play. In general, if it costs less than $40, it may not be very usable. Used ukuleles are fine, but Iook for a quality brand like the ones below.
Shopping at local shops are nice because you can try out the ukuleles beforehand. Some local shops in Berkeley are Subway Guitars (https://www.facebook.com/p/Subway-Guitars-61554332151492/) and Mark Walstrom's Timbre Folk & Baroque Musical Instruments has slightly larger ukuleles than the typical small soprano (https://timbrefolk.com).
Goodwill online has inexpensive ukuleles, but look for low shipping and handling expenses:
https://shopgoodwill.com/
A Nice Beginner (and Keeper) Ukulele
I personally have a Kala ukulele similar to the one below and am very happy with it, and would recommend spending a little more to get this nice ukulele that is pleasant to play and will last a very long time. Kala is a well-known ukulele manufacturer with a reputation for making quality ukuleles. It’s nice looking, has a nice tone, plays in tune, and has good action. After you play a good instrument for awhile, it will "open up," meaning that the tone quality improves and the volume can increase, which happened to my ukulele after playing it for some years. Of course, there are many other ukuleles that are more expensive and of higher quality available.
Kala Ukulele Package (Includes Padded Carrying Bag) $65
Less Expensive Acceptable Beginner Ukuleles
Hamano U-30 series
About $40, this ukuele is fine for beginners. They have a nice tone, good quality tuning keys (so they will hold their pitch), play in tune, and have good action (doesn’t hurt to press down on the strings).
Diamond Head DU-100 series
About $40, this is a decent beginner ukulele.
Books:
Rise Up Singing
This is the main book used in ukulele class. The spiral-bound version is best since it stays open better. Barnes & Noble sells it online for about $23: