You're describing mostly a hybrid or possibly "flat bar road bike".

Entry level bikes in that price range will have similar standard components. To ensure the most standard (repairable/upgradable components) I would look for:

Threadless or integrated headset (no quill stems or anything weird there)
Square taper bottom bracket
Three piece crank
8-speed or more cassettes (ie freehub not freewheel)
Removable derailleur hanger, not part of the frame, not part of the derailleur
Quick release wheels

You'd have to look at specific parts on the bike for those entry level bikes weighing more than 10 kg. There could likely be extra in the wheels, saddle or crankset, common places where they go a little lower quality or heavier to keep the price down.

edited: you don't need these threads also with the same question - that's kind of spammy.
http://www.bikeforums.net/hybrid-bic...ke-advise.html
http://www.bikeforums.net/commuting/...ke-advise.html