Recommend me a solid, used Android phone that can run Jellybean

Since I'm attempting to dive into the world of app development, I need to learn. While I intend to start with iOS apps, I think ignoring Android would be stupid. It is the second biggest app store out there, and Android is, depending on your region, the most popular OS out there. I've used Android a bunch, to the point that I'm comfortable with my choice to use iOS. But, I've never personally owned an Android device. Anyway, I figure it would make sense to pick up an Android phone of some sort to get truly acquainted with everything... to better understand how the app store works and all that. But, there have been a lot of devices out there, and I could use some help choosing something. So, here's a big list of parameters:

- Used (think former flagship or something... I'll set a preliminary cap of 200 dollars). My friend just replaced his old HTC Desire, so I could potentially just borrow it, provided it will meet the rest of these parameters (which you can probably answer better than me).

- Unlocked, capable of HSPA 850, 1900 mhz.

- Can somehow take a microsim. I know it's possible to use a microsim in a phone that uses a regular sim card, you just need to align it properly.

- Is generally well made.

- Wouldn't mind a decent amount of built-in storage... 16gb would be good.

- Most importantly: Is easily capable of running Jelly Bean. I don't mind having to root it or whatever, since this won't be my primary phone anyway. But, the less tedious the process is, the better. Really, I want this to be as representative as possible of how Android functions today.

- Ideally not enormous. I really don't like the sheer size of the current crop of flagships.

So, what do you think?