If they are being considerate and giving adequate time for the old landlord to find a new tenant no harm no foul.

There is mold and mildew and different types of strains so more harmful than others.

Question should be, how is the seller harmed, did he lose marketing time toward the end of the summer and/or a sale?

The lawsuit, which alleged that the turf state laws harmed consumers by preventing access to the national market for commercial real estate brokerage and depressing real estate prices, was filed by a group of consumers, real estate brokers with Marcus & Millichap Real Estate Investment Services, a national commercial real estate services firm based in Encino, Calif. leading the suit.

Stress is very harmful and no amount of money is worth your well being.

Well rental income would be taxable normally anyway so there is no real harm done,

My business partners thought what's the harm...we don't plan on buying the house anyways, so, why not share the info. 

We all encounter those who seek to do us harm and as the the Irish say " forgive those that trespass against us but cruse them so we know who they are".  

Elisabeth, The military move out provision is not really for the tenant's benefit whatsoever as they already have that right legally regardless of what you say, so it is really just if you get orders to move back you can kick them out no harm no foul. 

Colton S. mentioned, there is no harm in getting prequalified with a lender.