Any animals added after lease signing must be cleared and written permission obtained from landlord and information must be provided to landlord prior to occupancy so that landlord may verify and consult with property insurer.  

But the question isn't whether it's permissible to get an assignment fee.

I looked into doing that a few years ago and I seem to recall that's permissible.

But Clay is right in that you'll want permission to lease property specifically written out in the lease, as any good land contract would prohibit it without approval.

The judge/attorney couple had been using a portion of their neighbor's yard WITH the neighbor's permission for years.