I tend to read more unusual literary fiction type stuff and sadly, my wish list is rarely available for Kindle from either of the 2 library systems I have access to (my county of residence in the State and the overseas military library system). However, Kindle lendability is still very new, so I believe that will continue to improve at least somewhat. I do allow myself some spending money for Kindle books. It may not be mustachian, but I look at this a lot like MMM seems to view organic and other special foods. I can afford to do it and I believe that reading makes me better, so it is worth it to me, but I recognize it is a luxury and would be one of the first things to go if we suddenly had debt (how does one suddenly have debt?) or job loss.
I would recommend, if at all possible, joining as many library systems as possible. Different areas have different eligibility requirements so you may well be able to get a card from more than one system. Since you'll be checking out online, location doesn't matter.
I have a Gen 2 Kindle for several years and loved it. I'd read literally hundreds of books on it with no issues. Sadly, it was stepped on during a move and the screen broke. I now have a Paperwhite, which I got as a gift when I needed a replacement. If I were buying on my own, I'd probably go with another Gen 2, used. The light in the Paperwhite is nice, but not really worth paying extra for when you can buy a clip on book light for about $10.
If you already have an iSomething, there is a Kindle app, which would have you a ton of money. But then you are reading on a backlit screen so you have to decide how much you read and whether your eyes will object to that.