I'd strongly advise against a home-made mains-voltage heater - where are you going to get all the exotic ceramics you need for insulation (mica?, alumina sheets or paste, etc etc)?
You need to be aware of the temperature dependence of resistance of nichrome - fortunately much less than many metals, but there is a dependence you need to be aware of.
Most soldering irons these days are low voltage for safety and convenience of temperature-control (solid state), but they are a heating element in ceramic insulation inside a metal tube usually I believe.