E2 advice needed - urgent

[uktousa2007]

Hello I am in the US on a J2 visa with my husband who is the J1 - our visa expires Feb 7th and although I have a pending I-140 I have a wait for 4 years for a visa (EB3). My husbands employer is sponsoring him for H1B but of course cannot apply until April 2007. So, we would like to apply for an E-2 visa. Can we apply from within the US while we are on our current visa's? If so I would like to know the minimum amount to invest, I realise it depends on the type of business. My husband is helicopter flight instructor so we are thinking of leasing a helicopter and developing a flight school from scratch however I think that although this does not actually need much of an investment to start to authorities may think it does. So we are thinking of an agency that places helicopter pilots in jobs - could this been seen as having little to no overheads and is this a viable company for EB2? My husband already runs the flight training school that he works for.

Also, any idea where the E2 is processed in the US and how long processing takes?

Thanks to anyone with any answers!