Etching PCB's at home is not difficult, but it does take some practice to get it right. Large boards and small components make it especially difficult. It is likely that it will take a few tries to get the process right, so I recommend making some smaller boards first to gain experience. Here are some tutorials on making boards:
Really the only thing you need to buy to make PCBs is the etchant, which will be around $10 USD. This assumes you access to a laser printer and photo paper or use magazine paper.
The total cost of making an entire RepRap board will depend on where you get the parts. If you don't have access to parts, buying in small quantities if not cheap. You will probably not save money over buying a kit.
As for tools, cheap soldering irons start at $10-20 USD and will work in most situations. More expensive soldering stations will have better temperature control, more available tip sizes, perhaps adjustable temperature and more power so it will heat up faster and you can solder larger pads and parts.
Digital multi-meters also start in the $10-20 USD range and go up to many thousands of dollars. Cheap DMM's will work most of the time, but won't last as long and are more likely to be damaged if you touch high voltage. You can get pretty good units for $30-50.
I hope this answers your questions.