What is a one-sentence summary of the following article?
A future landlord wants to know how long the person has been your tenant. Go through your paperwork to find the dates. You should have a copy of the leases the person signed. If you don't have any paperwork, look through your bank records. Check the months you have deposited rent into your account. A future landlord also wants to know how stable the tenant is. Accordingly, check your records to see that they paid the rent on time and in full. If not, write down how late they were with the rent payment. Did you have to pester them? Did you have to give them written notice that they were late? Your reference should also mention whether you received complaints about the tenant, especially from other tenants. If there were complaints, note what they were about. Also think about how polite the tenant was when you spoke to them. Were they agreeable? Angry? Did they address the problem? Pay attention to complaints about pets. Many landlords are hesitant to rent to pet owners. Were there complaints about the tenant's dog or other pet? You should also note in your letter whether the tenant left the property in good condition. Was it clean? Did you need to make repairs? Did the tenant cause a pest infestation? Tell the tenant you want to check the property before writing your letter. So long as the tenant is still living with you, you must give them notice before entering the apartment. Check your state law for how much advance notice you must give. Writing a negative reference for a bad tenant invites headaches. For example, the tenant might be angry that the reference isn't positive. Also, they may dispute the accuracy of your letter and claim the negative letter prevented them from getting a place. You can refuse to write a character reference altogether, which is usually the best choice in this situation. Similarly, you shouldn't give a bad tenant a positive reference letter. If you lie to a potential landlord, you could be legally responsible.

Summary:
Confirm the dates of the tenancy. Note if the tenant paid their rent on time. Check if any complaints were filed. Check the property. Refuse to write a negative reference.