Someone else will probably link it for you but I'd strongly suggest a thread by Leftie Biker, sort of a buyers guide/tips and tricks for Leafs, particularly older first-generation Leafs.
I had 2 gen1 Leafs, a 2012SL and 2013S and had very little issues with them, all in all a decent cheaper EV. I never had any heater issues but I do read an occasional post of someone who does and it can be very costly to fix, almost to the point of it not being worth it to fix, so if a working heater is important to you(like it would be for me in MN) I'd strongly suggest verifying it works, even though it's now summer and you might not think of it.
As I'm sure Leftie's guide suggests, I'd probably skip anything older than '13 model year and even then if you live in a warmer climate not anything before April of '13 build date as Leafs older than that tend to suffer bad battery degradation, especially in hot areas but also more moderate climates such as MN. The pre '13 Leafs also had other issues I didn't like, such as no SOC% indicator so unless you have a very hard-to-find aftermarket display or Leafspy installed on your smartphone. you will only get the wildly inaccurate GOM(Guess-O'-Meter) display that comes on the car, telling you how much range you have.
All in all I think a older 1st gen Leaf is a pretty decent safe low maintenance car for a first-time driver if they can live with the very limited range of 60 miles or less and even down to 30 in the very cold and if the battery is degraded and the user keeps up on keeping the battery charged, it's not such a good choice for people regularly driving across a larger town or for sure out of town. The batteries rarely fail they just get less and less miles from the new 70 mile range.