You haven't said how much metal you want to heat. 700 degrees isn't a problem if you only want 1 gram of molten. The amount of power is the specific heat of the metal multiplied by temp and mass plus allow for temp loss from furnace. Look up specific heat in metal or element tables. Work out total energy, then divide by time to get power needed then allow for efficiency of energy coupling with heating coil. Suggest you look up induction heating company and go visit, smaller ones will sometimes show you through. You will be shocked at how much power is needed. I've seen medium sized induction furnaces of 20kW power draw from mains electricity. Gold or technical alloy companies will use small induction furnaces to melt and mix alloys very cleanly usually under inert gas shield. That will be the sort of scale of equipment that might be in the area you are looking at. Search for precious metal smelting equipment. It's always useful to find out what commercial companies do out in the world. the internet is your friend. Good luck, Colin