Tricky challenge that one. I've done the odd miniature model built from scratch from green stuff (sort of taking Warhammer miniature conversion a step further), but it does require a lot of practise and "supplementary material". Green stuff isn't cheap. Looks better when painted too.
Bronze casting is probably out of the question too
3D Modelling? Doesn't really give you anything to put on your shelf in itself, but if you create models/sculptures you really like, you can export it in a file and have it printed out on a 3D printer (they are a bit pricey still, but get better and cheaper by the year and there are companies you pay to print it out in quality plastic).
Are you aiming for small stuff, large stuff, actually building something or assembling and painting/customising something? Maybe Guarddog has a spare car for you to renovate