The bare minimum you need is: a daylight tank, a dark place to load it (e.g. changing bag or completey dark room), thermometer, developer, fixer, water jug or running water, fixer, a place to pour out used chemicals/water, and a place to hang the film to dry (this is the hardest part.) You need only two storage bottles: one for developer and one for fixer. (Buy "odorless" fixer to minimize complaints about the smell.) And if you use a liquid developer like Kodak HC-110, Ilford DDX or Rodinal mixed one-shot each time you develop, you don't even need a separate developer storage bottle - the unmixed concentrates are already in rather small bottles that have long shelf lives. To mix small quantity one-shot working strengths, you just need an oral medicine syringe (designed for giving liquid medicines to babies, found in any drugstore) and a measuring cup/beaker. Some would say photoflo for after wash drying is also mandatory which would add one more bottle.
Originally Posted by LowriderS10
Chemicals are rather inexpensive: $20 will buy you more than enough to develop 20-30 rolls of film. Small developing tanks and reels are often just given away or very sold cheaply. A dial thermometer will be the biggest expense at $20-$25 if you can't find one used.