macos imac 18 mojave

Hi! I'm trying to help out an old colleague of mine. She wants to buy a new iMac, run Parrallels 18, run Mojave (or an earlier version) under Parrallels, run Adobe CS 5 or 5.5 under Mojave (or an earlier version). Which iMac should she buy and which OS should she run so everything will work...