It has not been well maintained over the last 10 years and is beginning to deteriorate. 

Spring deterioration is normal wear and tear and hell no a tenant is not responsible for maintaining the springs on a garage door.I tell the LL to pound sand..... prove there is was negligence or a commonly accepted documentation that garage door spring maintenance falls under tenant responsibility for general unit maintenance. 

Quote from @Maria Holodnaya: Maybe they are trying to clean up a neighborhood that's been allowed to deteriorate for too long?

You'll also want to ensure you have a good property manager to look after the upkeep of the property if you are not there to notice anything deteriorating or which may need attention.Creating an LLC in California would cost you a minimum tax of $800 every year.

Gentrification in older urban areas with rundown housing stock might be the only thing that prevents all of that rundown housing from becoming unoccupied, and eventually being razed due to their unsafe conditions as they continue to deteriorate while unoccupied.

The landscape is crowded with these nightmare properties that sellers allow to deteriorate.

High dividends with potential of the assets deteriorating in price over time. 

But there has not been any noticeable price deterioration. 

I can't imagine why she'd want this house to just sit and deteriorate.

I recommend that as one of the upgrades to consider as a one time cost rather than cleaning and replacing carpet every few years and your cleaners will love you too.You also have to consider these are spec built homes from large National builders like Lennar, Pulte and DR Horton (for the most part), so they don't have high end finishes so you will see things like the grout in the showers deteriorate, exterior paint put on thin, screen doors with broken handles, microwave door handles broken and fairly minor things like that.