How much do you want to spend? 4x5 is a lot cheaper for a camera, film, chemicals, lenses, film holders, tripod, etc... an enlarger can cost you as little(say $100 for a beat up Omega D-II) to as much as you want to spend, and add to that the cost of a good enlarging lens. An 8x10 costs more, but those negatives are awesum! With careful shopping you can cut your costs down quite a bit, but nowhere near a 4x5. The alternative 5x7 as others have mentioned, is a very viable option. Some cameras, like the Agfa, allow the use of both a 4x5 and 5x7 back and are light enought to use a heavier duty medium format tripod. They are not uncommon to be found with a lens for about $200. A few used film holders, dark cloth, and loupe and you're in business. For 5x7 film try Freestyle---100 sheets of APHS-ortho-for $21 or Arista Pro--if its not Ilford, I don't know what it is--25 sheets-panchromatic- for $21. Good luck!