Mainfrm & Mid Rng Maintenance Potential

Hi all

i’m absolutely new to this and pls pardon me if i ask for something very basic.

I am currently evaluating the potential involved for maintenance, enhancements, porting etc on Mainframes and Mid-range comps. Gut-feel says there is a huge potential, but i’m not able to pin-point
* which industries to target
* which industry has what types of mainfrms/mid-ranges (a 80-20 rule)
* what kind of support would companies be looking for
* any numbers that one can project and look fwd to

Can anyone help me out? i tried the search engines…havent yet been succesful.

Thanx.
Ananth