For finding used equipment, I'd stay away from books as numbers will be outdated. Stainless steel prices change all the time, and used equipment isn't immune from stainless steel commodity prices. Instead, contact Brewing Equipment dealers such as Ian Day at North American Brewing Services, Vince Cottone at Sound Brewing Systems, or Jason Ager at Ager Tank & Equipment. Last year around this time I was looking for a used system and was finding it difficult to make an offer on one as they were usually sold within a few days of being offered for sale. I doubt that's the climate today with malt and hop shortages. Also, check ProBrewer Classified Forums. Sometimes used systems are listed on the Brewers Association Forum, but you'll have to sign up to the Brewers Association as a Brewery in Planning (around $300) to get on the list, plus you get a subscription for New Brewer magazine and get a better rate for the Great American Beer Festival and Craft Brewers Conference. Speaking of the Craft Brewers Conference, it's coming up this April in San Diego, and I'd recommend any prospective brewery startup to attend the seminars and get to know your suppliers.
The cost of brewing systems vary widely based on brew length (how much wort is being made at a time), how many vessels, what's included (pumps, hard piping, heat exchanger, etc.), steam or direct fire, whether the steam boiler (for a steam powered system), fermenters and a glycol chiller are included, and so on. For a 2-3 vessel 15-20 bbl system with everything you need, plus an acceptable amount of fermentation/cellar capacity (let's say 60-90 BBL's worth) will run around $150,000 - $200,000. A new system with everything you need will run around $300,000 from the value conscious suppliers. I'm sure there are better deals to be had, but this is just a general number you could expect.
The lowest amount you could expect with everything you need would be $50,000 for a bare bones 2 vessel system of 5 BBL or less. You can expect to use hose to connect your vessels during brewing, and you probably wouldn't need to spend too much on malt handling (augers, large mill, etc.) for this size of system. I wouldn't recommend a system under 15 BBL as you'll find making a profit in this industry is not easy. Having to brew 5 times a week on a 4 BBL system is a lot less efficient use of your time than brewing once on a 20 BBL system. If that's all that can be afforded, and it's just a starter system, then it might work for you. Just don't expect to make any money, and prepare to lose a bunch.
You could spend less on a single vessel malt extract kettle, but I'd stay away if your goal is to make great beer. If you're looking to spend less than $50,000 on equipment, I'd consider mead making as you'll only need a boil kettle and fermentation space. Plus, mead is increasing in popularity and there are very few commercial mead makers today.
As for what the vessels are used for-- I'd recommend getting into homebrewing and visiting breweries! I'll give a basic overview from what you need from the beginning of a brew to the end:
Malt-- You'll need a way to crush the malt, unless you intend to buy pre-milled malt. A 2 roller mill is what is used for a smaller system (under 30 BBL). You want to size the mill so you can mill enough malt to dough in within 30-45 minutes. If your batches used 2000 lbs. of malt, you'd want to get a mill that could handle 3000-4000 lbs. of malt per hour, or get a grist case to receive and hold milled malt prior to mashing.
Water-- At a minimum, you'd have an activated carbon filter to remove chlorine, organic compounds, and some hardness from your water.
Mash tun / lauter tun-- The mash tun is used for mixing malt and hot water in order to aid in conversion of starch (in malt) to sugars through the use of naturally occurring enzymes contained in the malt. Brewers yeast mainly metabolizes simple sugar, so this is why the conversion of starch to sugar is critical in brewing. The lauter tun is a vessel for separating the solid malt particles from the liquid wort. Smaller systems have a combined mash tun / lauter tun, meaning the same vessel is used for starch conversion and for drawing the wort from the grain.
Boil kettle-- Once the wort is drawn off from the lauter tun, it is brought to a boil. Hops are added at different intervals in the boil for bitterness, aroma, and flavor. If you had a malt extract system, you would skip to this step. You'd add malt syrup or malt powder to filtered water, mix, bring to a boil, and add hops as usual. There are even no-boil extract systems where the extract is already hopped, but expect the beer to be pretty nasty. A typical boil is 60-90 minutes.
Whirlpool-- Some systems have a dedicated whirlpool, which is used for recirculating the hot wort in a centrifugal fashion, bringing the hop / protein solids to the middle of the vessel for easy separation of the liquid. Most systems just include a whirlpool port on the kettle to perform this function in one vessel. The advantage of having a separate vessel is when brewing multiple batches at a time, you can get the first batch out of the kettle and begin lautering / boiling your second batch. This would shave 1 to 2 hours from the total brew day if brewing two batches that day.
Heat Exchanger-- For sanitary and flavor purposes, you need to bring the wort down to 50-70 degrees fairly quickly once the boil is finished. A stainless steel plate heat exchanger is typically used. Cold water runs through one side, while the hot wort is pumped through the other side, resulting in a cooled wort once it makes its way through the heat exchanger. This is directly pumped into a fermenter.
Fermentation-- Typically cone shaped fermenters (cylindroconical) are used for fermentation, as their height takes up less of your valuable real estate, and the cone shape aids in yeast collection and trub dumping. This is where the yeast is added, and the yeast converts most of the sugars in the wort into carbon dioxide and alcohol. Fermenters should have jackets for running chilled glycol in order to control fermentation temperature. Alternatively, you could have a temperature controlled room for regulating fermentation temperatures, but it'll be less precise and result in a higher electricity bill.
Cellar-- Once fermentation has ended, typically you'd have a brite beer tank for beer maturation, cooling, and carbonation addition. Beer is packaged (into kegs / bottles / cans) from this vessel.
Bottling / Kegging / Canning-- My numbers above didn't include this part of the brewing process. Kegging is usually the least expensive option, especially at the beginning when you don't need many kegs on hand. Bottling and canning lines can be very expensive. If you're looking to make a bottle conditioned beer, you can spend a lot less because your equipment doesn't have to deal with carbonated beer and reducing oxygen pickup is less of an issue. Of course, you could also use homebrew equipment for the bottling of carbonated beer, but don't expect to pay the bills by packaging that way (it's very slow).
I hope this info will help Nick and others!