I would suggest at a minimum that you read a few books. Charles Stratton's work in the "For Collectors Only" series is a pretty good place to start. You can find these on Amazon. Here is one:
http://www.amazon.com/exec/obidos/t...f=sr_1_1/002-1479304-6932047?v=glance&s=books
There are too many Enfields to even start to touch on here, but since I am partial to No4's (as you might have guessed...
) I'll give you a quick primer....
Me, I don't have a No4Mk2, so a Faz Mk2 is on my list right now. However, while they are nice rifles, they aren't as interesting (to some) as the WWII era Mk1 and Mk1*'s. As for those, the best is obviously one in nice original condition, but a FTR (Factory Thorough Repair, aka arsenal rebuild) is not too bad either. A private restoration can be very nice looking but obviously holds the least collectible interest of the three.
Also find out what year it is. 1943 and 1944 are the most common for WWII rifles, and 41, 42 and 45 rifles (especially 41 and 45) are more interesting. Wartime production was big in the US and Canada, with Savage and LB making the most rifles, and the three Brit arsenals together making fewer than Savage and Long Branch, however many here in the US enjoy the "American-ness" or at least "North American-ness" of Savage and LB rifles so they seem to hold their own pretty well all other things being equal.
As for where to find them.... You have to be patient and look, but people find them at gun shops, pawn shops, and gun shows. Not as common as they once were, but still can be found. More reliably, you can find them on auctions, but be careful or you will get taken to the cleaners. A lot of the auctions are over-priced out of the gate, and those that aren't often get bid up. If you are willing to pay for real quality and peace of mind to know that you are getting what you pay for, you should try someone like Brian Dick at
http://www.bdlltd.com .
Edit to add: There some Enfields that recently hit AIM and Century. I think it has been determined that these are Indian rebuilds. While these are still decent rifles, and one of my best shooters is an Indian rebuild, they are not nearly as collectible, so just be aware of what you are getting.
Probably the best C&R "bargain" right now still has to be the Yugo 59/66 SKS. While not very collectible in its own right, it is a fantastic semi-auto at an unreal price. When these things are gone the prices are sure to rise steadily.
This is sort of a random brain dump, but I hope it helps!! Also, be sure to check out the C&R forum linked in my signature.