HELP, nightmare tenant left trash in duct work!

[Melissa Kaatman-Boettge]

We bought a duplex a few months back, one unit was empty and the upper had a tenant. The tenant just moved out in early July, so we've been rehabbing the unit. Yesterday a duct guy came and discovered that one of the vents was missing it's cover and it appears anything and everything has been thrown into the duct. He was able to get out socks, toys, a shoe, curtain rod and even a wallet with $10. The problem is there's still a decent amount of stuff in there and it won't budge! It's about 5ft down from the vent in the upper unit. I'm worried our only option will be to cut through the wall and duct in the unit below to access the clog. Anyone have a better idea?