Start by talking to them and explain that even with the warning, things are not improving and then serve them with notice to cure. 

Below is a chart showing the average reclassification percentages by property type.Apartment Building - 20-40%Conference Center - 25-35%Fitness Center - 22-45%Assisted Living Facility - 22-45%Golf Course - 28-60%Theme Park - 16-22%Grocery Store - 20-45%Hospital - 28-40%Auto-Car Dealership - 29-35%Hotels - 20-40%Research Facility - 22-45%Manufacturing - 20-40%Warehouse - 20-30%Medical Office/Clinic - 22-35%Resort - 25-45%Mixed Use - 20-40%Leasehold Improvements - 20-80%Office Building - 20-30%Retail Strip Mall - 18-40%Winery - 18-25%Restaurant - 20-80%Bank - 30-45%Are there any other types of properties you would like more information on?

Austin's first 'Tesla Solar' neighborhood explainedPanels, batteries coming to new homes in Easton Park master planned communityThe Article reports on a new partnership between Tesla Energy, Brookfeild Asset Management and Dacra.

Filters, refrigerator filters, batteries for smoke detectors and fan remotes, light bulbs, etc.Your list is pretty thorough though, I'd only add to make sure you're doing a semi-annual HVAC maintenance.

I do like the peace of mind that comes with the knowledge that the work has gone through the official permitting process, as this significantly improves the odds that is was done correctly and will not be a problem later.I am wondering if it is a good idea or a bad idea to purchase a property with significant recent unpermitted work if I can get it for enough of a discount to have all the work inspected, fixed if necessary, and perhaps retroactively permitted. 

A lender might be able to use the rental income to improve your DTI and get you approved for a higher amount, though it may only be a portion of the rental income since its been less than 2 years.

has your credit rating improved?

Value-add - first 2 months improving the paint/decking/driveway/gutters/drainage/etc.

I mentioned this to my friend that owns the company and he suggested that maybe my new tenant would be able to make improvements as he previously did construction.

A local realtor estimated that, after a few more cosmetic improvements, 2 weeks of ads, and 2 consecutive openhose weekends, we would likely gross $336,000 to $355,000.