As has been said elsewhere collecting military surplus firearms really gets under your skin once you start doing it. The fluctuations in the importation laws and regulations as well as the demand for particular firearms can make their prices and availability vary widely. My personal approach to collecting back in the beginning was to buy up everything that was cheap. That led to me owning 31 Mosin-Nagants, about 21 Mausers, and some 9 Austro-Hungarian M95s as well as assorted Enfields, Martini Henrys, and Eastern Block air rifles. Later on I realized I had gaps in my collection, and spent more than I would have liked to acquire M1 Carbines, a couple Swiss rifles, a French M36, an Italian Carcano M39, and assorted military handguns.
  A more disciplined approach would be to identify up front what your goals are, then pursue them as the opportunity presents itself. May I suggest the goal of many a military surplus collector is to have a representative sample from each of the major participants of the Second World War. It's easiest to start with the ubiquitous Mosin-Nagants. They're still inexpensive, and you can get the 3 main varieties (91/30, M44, and M38) without breaking the bank. The Finnish versions of these rifles cost more, but are also rewarding to collect.
  If you're going to be getting surplus firearms, you really should get a Curio And Relics license from the BATF. It allows you to receive firearms in the mail or via UPS without going through a gun store and paying $45 each time you get one. The C&R license costs about $30, and is a minor hassle to process, but once you have it you're golden. Trust me on this. I bought over 75 guns within 2 years of getting mine.
  Mausers are the bomb for collecting. Aside from being generally well made, there is an infinite variety to choose among. The Mauser brothers went out of business early on, and they sold out to a Jewish fellow named Ludwig Loewe. Just before the turn of the century in order to deflect interest in the firm's Jewish ownership, Loewe renamed the firm "Deutsche Waffen und Munitionsfabriken" and cranked out Mausers for nations all over the world including a LOT of South American countries. The long Chilean Mausers in 7mm are things of beauty, as are the ubiquitous k98s with Nazi stamps.
  In fact the Nazi k98s are an excellent place to go now that you have your Mosin-Nagant. Another suggestion is to get a Persian Mauser. They are gorgeous, and they look like they've been very lightly used. I picked one up for $250 on the secondary market (marketplace forums).
  This brings me to another Mauser variant that's worth looking into: The VZ24. The Czechs began making Mausers at their Brno facility in 1924 under the model number VZ24. It was a short version of the pre-WWI Gewehr 98 model that was shorter and handier. The Czech Mausers I think are better made than the German ones, and they sold them all over the world. You can get Turkish VZ24s, Brazilian rebel VZ24s, Romanian VZ24s, and the list goes on. The Romanian ones are also in beautiful condition, and mine is one of my favorite shooters.
  Also as was stated above the Yugoslavian Mausers are still available and relatively inexpensive. They are not parts-interchangeable with other Mausers, but they're nice guns nevertheless.
  Now something to look for: Rifles that have matching serial numbers on the receiver, the bolt, floorplate, and any other numbered part fetch a higher premium than unmatched guns. That having been said you're unlikely to encounter a K98 with matching numbers in your price range. Most were captured by the Russians, then in the clean-up process their parts were mixed and reassembled. These are called "RC" or "Russian Capture" K98s, and they're just fine as guns, they are collectible - specially the ones with original Nazi stamps on them. Many of my Mausers have mismatched serial numbers. I love and shoot them.
  The Austro-Hungarian M95 is a good gun to buy, but there are few variants available. They're rapidly disappearing from the market, so if you want one get it soon. They are interesting because aside from the fact that they armed the Austro-Hungarian empire, they were mostly used in both world wars, AND they use a peculiar straight-pull bolt that really sets them apart. Be warned though: They use 8x56mm ammo that is hard to find. You may have to reload this round.
  British Enfields are also on the way out. The SMLE is still available on the secondary market, but few importers still have them. Again ammo is hard to get, but they have very nice triggers, and if you want the WWII set, you gotta get one. This one was made by Savage for Lend-lease to England in 1943.
  Of course everyone wants an M1 and an M1 Carbine. Nuff said about that.
  The Golden Age of Military Surplus collecting is rapidly coming to an end. Five years ago any retailer that sold guns carried Mausers, Mosin-Nagants, SKS's, M1 Carbines, Austro-Hungarian M95s, and Lee-Enfields. These days few retailers carry them at all, and the ones who do have only Mosin-Nagants and only the more common 91/30s at that. What's worse is the prices have gone up for everything. Having said that, all of these rifles are still available, but you have to look a little bit to find the ones you want. It's OK though, because 20 years from now when ALL the military surplus guns are gone from the market, collectors will thank their stars that they bought up what they did when they could.
  * This is My Rifle *