Why are you insisting on a single pet?
Cats are less socially dependent than dogs, but they are still social creatures who prefer to not be alone for 8+ hours a day.
Either work from home so you can provide their social needs, or get two cats so that their social needs can be met even when you're not there (also makes taking vacation and travelling easier).
Seriously why would you insist on only a single pet? That seems insanely arbitrary.