I would certainly recommend residential investment in Elgin- there are many builders offering awesome incentives and if your Realtor is highly connected, they may already have pre-negotiated deals on residential units.
As for commercial, it depends on what kind you are trying to invest in. Elgin is an old town but a new city if that makes sense- if you're interested in commercial investing, the city is certainly growing rapidly and becoming an alternative to the City (especially as Manor fills up, attracting people to Elgin).
I like your long term thinking- you'd be surprised how many people aim to make a million dollars overnight! :) (Sorry for the delay in answering, I am new-ish on Trulia!)