I hope you do ok,in addition to model engineers,there is also a market in castings for vintage stationary engines,and full size steam traction engines. Stationary engine work is mainly cast iron and bearing bronze,flywheels ,pistons ,trolley wheels,cast iron silencers. crankshaft bearings etc. If you start a business get organised,with small one offs do not loose customers patterns,if customers borrow parts from other enthusiasts so that they can be copied dont loose or break them,or accidentally put them in the melt thinking they are scrap,keep delivery promises, all of these problems have been experienced by myself and friends in the past.