Do I need to do that or anything to ensure our rental property can stand up against any challenge from the tenant (not that I have any reason to believe they have an issue or will take an issue at this stage).

Do what others won't and you will stand out.Hope that helps a tiny bit.Good Luck!

But as I look at my assets stand alone, this one entices me to sell (except the tax implications).

Looking over the building's expense, the one that stands out is the water bill.

I ran into this exact same situation in 2008 with a rowhome on South Carey st (aka SCAREY st) and the only thing that saved me was i did a lot of the work and acted as my own general contractor. 

When you have your owner agent, at least they want to maintain a good standing with you for future business and referrals.

@Maurice Evans If the area was on the way up, then you might stand a chance to fix up and eventually get good tenants in there.

Also they sign the form, so in the event you get audited, they stand with you to help you through the audit.Nothing wrong with taking short cuts or hacks in life, but taxes is not the place to do it. 

What stands out to me is when an agent really shows his/her best interest in my decision.

Too many people take the stand of looking at depreciation schedules and think "eh it was time for a replacement" without bothering to look at the actual item to say "well that still had a lot of useful life left in it".