Oy. Proceed with caution. Unless you've got a very very nice $$$ apartment, I doubt you'd want to leave your apartment and more importantly, your furniture and possessions, with just anyone.
And read your lease thoroughly to determine if you can even sub-let. In some buildings, you can't. Also, how would maintenance requests be handled- would they need to go through you or can sub-letee go straight to landlord/super? Again, some buildings are pickier than others. Also, read up on your renter's insurance policy and how any incidents would be handled while subletter is there.
If you have luxury, doorman apartment, you may want to look into becoming a long-term vacation rental with a $$$ travel agency and have a series of tourists use your place for a couple weeks each.
Honestly, I know it's tempting to make a little extra cash while you're overseas, but nothing can buy peace of mind and you'll only have that if your apartment sits empty or if a trusted friend/family member can sub-let from you.