Welcome to the forums...this is a good place to start. You'll find a lot of info here covering the spectrum from beginner/hobbiest to pro. I suspect that your call for help has gone unanswered so far just because you've called out for a one-stop answer to a rather complicated question. I will show a few vendor links just as references to show you what some of the cost may be like. Don't jump out there and start shopping yet! Also, many vendors will let you return the products except mics and open software for a full refund up to 30 or 45 days. Check out their return and exchange policies. Although this close to the holidays, you might not get what you're looking for in time...you might be resigned to visiting the local Guitar Center...anyways....
Important questions...does your computer have a firewire port? If not, does it have spare or open PCI slots? More computer specification would be good to have as well (CPU speed and RAM). Most importantly, what's your budget? You said that this might be a passing phase so to me this implies you don't want to break the bank. You also mentioned that he plays guitar and sings. Possibly doing both at the same time I'm guessing.
The basics require a mic, cable, mic preamp, and an audio card in the computer (assuming you're wanting to record to the PC) and finally, some sort of recording software.
Starting with the mic(s)...I'm thinking two would be nice but it can be done with one...one would get you started. IF it were me...on a tight budget for two mics I might go for a package like this
http://www.guitarvision.com/mf/mf_frameset.htm search for Product #273168 . A better idea would be to post a new question on the forums in the microhopone section asking something like "help me buy a mic or two as a gift to be used for
acoustic guitar and male vocals for a recording beginner" and see what comes back.
An item I overlooked was something to hold the mics up...as a guitarist myself, I prefer boom mic stands. The cheap ones will work and if treated gently will last for some time and serve the purpose but be warned, the quality stuff runs up in price real fast. Again, on a budget yet functional
http://www.guitarvision.com/mf/mf_frameset.htm search for Product #452061. I'm gentle with my stuff and I've worn a few of these out in my time.
Microhpone cables...one for each mic if you use both mics at the same time...just search for mic cables...the tech description will show XLR connectors on both ends (one male and one female). I mention this because there are some with TRS or other connectors on them. Prices will vary but for entry level purposes...cheap cables will work for the first time go-round
http://www.guitarvision.com/mf/mf_frameset.htm search for Product #361707.
Mic pre amp...this is where things get crazy real fast. It's primary function is to amplify the weak signal output of the microphone so that the signal can be used by a recording device like a tape machine or computer. Many mic preamps also act as a power supply for the microphone (phantom power). Not all mics need this but many do. For the time being lets just forget the amp because there are all-in-one devices which incorporate mic pre amplifiers with audio cards (the last next item on the list).
Audio interface aka audio card. As in the case of the mic preamps, there are a lot of choices and options out there. This is the final stage for the audio as it goes into the computer for storage. IF it were me, and my computer had the minimum configuration requirements and a firewire port, I might look at the M-Audio 410
http://www.musiciansfriend.com/srs7/g=rec/search/detail/base_pid/701385/ which will serve as the audio card, micpreamp and phantom power source. You could also consider the Presonus Inspire
http://www.guitarvision.com/mf/mf_frameset.htm search for Product #241483 which "claims" to do the same and includes recording software. IF you don't have a firewire port, these devices won't work...we'll start talking PCI type cards which opens up a bunch of other possibilities.
Lastly, the recording software. There are freeware products out there...it's possible that you could get by at first without spending a dime but, better than that, depending upon the soundcard you get, often times a simple yet useable product is bundled with the soundcard. The software options go from simply to way over-the-top. It facilitates recording, playing back and mixing and other wise manipulating the recordings.
These are the barebone basics of what's needed and I've only posed a few of the many choices out there. Other people in these forums may have other ideas and ways of doing things which may be better suited to your needs. Answer the questions at the top and we can take it from there. I would also strongly urge you to read this
http://www.homerecording.com/newbies.html and also follow the links through out the article. There is also a useful search function which will help you look up even more info.
Welcome...hope we can help.