Your lessee would certainly be permitted to invite a quest or two for a reasonable periods of time.
But this free loader is not an invitee. He has taken up what can reasonably be presumed to be his immediate permanent residence. And not being signatory to the lease he is in effect trespassing on your property. And neither custom or convention allows him to do so.
Options: You can either demand that he pack up and promptly quit the premises, OR, if you find him acceptable as a tenant, have him sign on to an amended lease with himself as a contracting co-lessee and increase the rent to a level which reasonable compensates you for (as you correctly state) additional "wear and tear". Also any security deposit should be increased accordingly
Your legal grounds rest in the fact that even though the lease doesn't expressly restrict the leasehold to a single occupancy, it can be so reasonably be implied.
As for Ld's lame logic, there is no justification whatsoever to claim that that multiple use does not add to the normal deterioration and wear of the leased premises. Nor that such is not an factor in calculating the rental rate.
This response is entirely BS.
In the first place, Latigo is ignoring the fact that there is a lease and the lease controls. If the lease does not prohibit additional residents then you cannot prohibit additional residents, nor request additional rent or an additional security deposit. His incredibly lame argument about additional wear and tear is just that, lame...and the whole "it can be reasonably implied" bit is absurd.
In the second place he is also ignoring the fact that you ALREADY gave permission for the additional resident, therefore even if the lease gave you the power to accept or deny an additional resident its too late.
If you were to attempt to make demands upon your tenant that are not allowed for under the lease and the tenant refused, then your only legal option would be to file for an eviction. If you filed for an eviction under the scenario you have described, you would be laughed out of small claims court.
Seriously? Think about it? "Your honor I want to evict this lessee because she won't pay me additional money for an additional resident." Your tenants response would be "Your honor, the lease does not prohibit additional residents and besides, I asked her permission and she said it was okay". The judge would totally be annoyed with you for wasting the court's time.