What NDS is best for homebrew? How do I hack it and what do I need?

I'm new to the DS. Actually I don't even have one yet but I want one and am planning on getting a used one in good condition. I bought a used PSP 1000 (it's been going strong for a year now) and hacked it and now I want to do the same with a DS.

I just want to know which DS is best suited for hacking, what is this r4 thing I keep hearing about, an what does it allow me to do?

Is the NDS homebrew scene as active and as good as the PSP homebrew scene?

I love homebrew, especially ebook readers (and comic book readers of course) and the NDS double screen would be perfect for ebooks. I looked around and the DS does indeed have a couple ebook readers. Are they good? What about comic book readers?

N64 emulation: Possible on the DS? I'm assuming no since it's not even that optimized yet for the PSP or even perfect on PC.

What emulators run well? GBA, SNES, GENESIS? I can emulate all that on my PSP pretty much fantastically, but if something were to happen to my PSP I'd like to have a backup with similar multi-media functions.

I'm not made of money so I don't want to just buy another PSP. With a DS I can also play DS games which I can't on PSP.


Can I watch movies and listen to music on a DS?