More information I'd previously posted on another forum:
Over many years I've set up 6 darkrooms for myself and one for a friend. It can be expensive, especially if you listen to salesmen who work on commission or instructors who have big school budgets. It can also be inexpensive. First, the function of the enlarger is to hold the film, the lens, and the photo paper in the right relationship, and evenly illuminate the paper. It doesn't take much of an enlarger to do this. A filter drawer for variable contrast filters is desirable. So is sturdy, vibration free construction. Enlargers can get out of alignment. Some have adjustments to correct this. Some others require some heavy-handed corrections. The enlarging lens is another matter. Don't count on the lens that the manufacturer includes with the enlarger to be high quality. Some inexpensive lenses do fine. Usually it is better to stick to the top brands. I'm partial to Nikkor, but, for large format, get by with the ancient lens that came with my primary enlarger. A good enlarging lens is a lifetime investment. Fortunately, most modern enlargers use lenses with the 39mm Leica thread, so upgrading the lens is usually easy. Another consideration in enlargers is the maximum size film you will ever use. Enlargers for large film usually work well with smaller film. The reverse is not true. If you never intend to shoot film larger than 35mm, there's no need to get a larger enlarger. If you might move up to medium or large format, get a suitable enlarger now.
Half of my darkrooms haven't had running water. Milk jugs are great for storing water at room temperature, and waste water and used chemicals can go out in a bucket. Even in a darkroom with running water, some water should be stored at room temperature if you develop your own film. It's much easier than mixing hot and cold water to the right temperature. You'll need a tank and reel for developing film. Some plastic reels are initially easier to load, but stainless steel reels are worth mastering. Tanks come in sizes that will hold from one to eight reels. Having several sizes is advantageous for those who develop large and small bunches of film. Since stainless steel tanks and reels last a lifetime, they are a good investment.
You'll need some kind of timer. A cheap clock works fine. A quartz clock that ticks once a second lets you count seconds while manipulating images while enlarging. I've rarely used anything but such clocks in 40 years of darkroom work.
Finally, the most valuable asset in photography is knowledge, not equipment. If you understand how things work, you can often improvise or do without. Talk to as many people as you can about your problems. Some people on this board have probably already solved those problems. A few camera store people are also knowledgeable and sympathetic photographers who will help you cut corners when setting up your darkroom. Most answers can be found in books. Double check on any advice, if possible. Some of the "experts" who write books are more interested in selling the books than in getting the information right.