Transfer my iPad to different user account on same computer?
Why not tether the iPad to iCloud, then it doesn't need a computer at all? If you do that and turn on backups, you can then set it to manage music (or media, if you do videos too) manually, and then you can drag stuff on and off from either computer, and none of your purchases will be lost. 

When you plug into the new computer it might ask you to authorise your account but you can have up to five devices or something so that shouldn't be a problem.