The correct answer is:
Whatever it says in the lease.
If it is not addressed in the lease, then they can stay over 7 nights a week as long as they pay bills at another address and they have their possessions at another location and they have a different mailing address.
Most leases only mention that the tenant may not "sublet" the property without the landlord's approval, and even the CAR lease does not specify when a guest becomes a resident. If you live in a homeowners association, some of the homeowners association's rules will specify that a person who stays over more than "X" times per week is a "resident", and that rule will apply to you as a tenant even if the information is not contained in your lease. In most cases, provided your friend has their own home and maintains the same as their principal residence, I find it difficult to categorize that friend as a resident even if they stayed over every night. However, this issue sounds as if it is yet another point of contention between you and your landlord.
You know, with all of the issues that you are having with the landlord, I have to ask why you continue to live there? It is obvious to me--as it must be to you too--that the landlord is doing everything possible to get you to leave the property. If you wish to stay there, you may need to amend your lifestyle to fit the landlord's requirements or work with the landlord in resolving this issues. If you cannot effectively communicate with the landlord yourself, contact your County Housing Authority and ask to have assistance in mediating your problems with the landlord. There are often free services that will work with you and the landlord to resolve issues.
Grace Morioka, SRES, e-Pro
Area Pro Realty