Depends, of course, on what you want to spend. Let's go the cheap route to start with.
Your post mentioned only a recorder. Realistically, you'll need more gear than that.
You and he will want to start with either a cassette or digital 4-track machine. Then you'll need mikes or a direct-input device, to record the guitar sound; and an amp and speakers to play it back through; plus a second recorder to mix it down and master to. A CD player is great to have if he wants to record himself playing against CD backing tracks.
Assuming you know all that... check out buying clean used equipment. Used 4-track cassette recorders - good ones, like the Tascam 424 - are coming down to $200-$250 used. People are ditching them in droves because low-end digital is getting so cheap.
I started on a clean used Tascam 424 ($200)and hock-shop amp, speakers, and an old stereo cassette deck for mixdown. Total cost, $500 out the door.
E-mail me and I'll send you my standard "article" on the gear you need to get going - on the cheap - in home recording. I am a regular on the H-C Guitar Forum, and I saved the piece because I kept getting so many requests for it.
The "
Line6 POD" that another user mentioned is a terrific piece of gear for direct recording of electric guitars. Highly recommended for electrics, but you mentioned recording acoustics too. You'll need a mike for those.
Beware and take care - this hobby is addictive! I ended up getting a low-end 4-track digital MiniDisc recorder ($500 used) and better monitors and a better amp and a POD and...
K-wey
barrefly@hotmail.com