I modelled happily for years in 4mm without any power tools or machine tools. You just go about things in a way that suits your capabilities. I've been a relatively late adopter. Started with an old Hobbycraft lathe which wasn't much used. It was the urge to have a go at 7mm that really steered me to machine tools. It seems to me that 7mm is a cross over point between model making and model engineering and there's more value in having such tools at that scale and bigger. And once you have lathe or a mill/drill you find it enables you to do stuff you'd never have contemplated before. If you've been thinking about it I'd encourage you to have a go.