All for this idea of Nels, Model steam engines are an excellent place for a home shop enthusiast to begin, And at the end of the day (God willing) one can have a nice example of ones work which can be a talking point and a further example of ones achievement which will engender pride in ones ability.
This level of the bar on your model can be set at whatever skill level one is capable of achieving and also will be influenced by the range and accuracy of ones shop equipment, Steam engines are fairly long suffering machines which will still operate even if in a sub finished state, This should not be taken as an excuse for poor workmanship, One should strive for a higher and higher goal as one progresses
It is a good thing to begin building ones first model from bar stock, as any mistakes are not as expensive as ruining an expensive casting There are a lot of good designs out there the Late Edgar T Westbury , had in the model engineer in the late 1950 era a really pleasant little horizontal engine for the beginner, These little machines can also lead on to one building up an interest on the history of the big engines formerly used in the past industrial field before the advent of electrical power.
I have recently been looking at the excellent designs of models by an American firm P.M. Engines I think? Really pleasant little machines and well proportioned.