well it's definitely an option...
personally I think that if you want a modular you are better just going straight to modular...
starting small is a very, very good idea - but that doesn't mean that the case has to reflect that - a slightly bigger case is always going to beat a tiny case economically - and experience points towards the fact that modular is fun and more modules are more fun - there's a reason they call it eurocrack!
saying that there are no wrong paths - just some are more expensive than others - buying used in particular will save money but only because if you realise that you are on the wrong path you'll have lost less if you come to sell it.. not that I've ever sold any modules - I just accumulate - that module that wasn't working for me 6 months ago does now as I have xyz module to plug into it, etc
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities