The more solid surfaces in a rental, the better.

Obviously there is more to maintain (three roofs instead of one, more exterior and interior wall surfaces for painting, cleaning, more soffit vents, more piping, more of something to go wrong), and also the maintenance is non-standard, as each cottage has it's own unique plumbing, electrical, AC, ducting, sewers, water supplies...versus in a standard 4-plex all the units have "similar" layout and the issues are more predictable and less challenging.These cottages are not on a very large lot that can be subdivided in the future.Would you ever consider buying multiple stand alone structures like this if there is no price advantage versus a 4-plex on a per door basis?

Install a corian slanted sill for water drainage and install a tub with tile surround. 

Street view shows a drainage ditch going right through the middle of the property.

s advice to use the HELOC to pay off the high-interest portion of the $40k.And while without knowing the market your looking to buy in or the specifics of your debt I can't be sure, on the surface it seems almost irresponsible to do anything else. 

Thinking of probably buying these sliding mesh doors by Meshtec I found. https://www.walmart.com/ip/Titan-Security-Surface-...They are ridiculously expensive but will look so much better than the security bars.

So even though the surface looked one way the violations changed the dynamic significantly.By the way , I know you are experienced and probably have these things covered but .... just in case.Good Luck.

Structural damage, bad roof, bad boiler, bad drainage.

Fix the problem, remove the sheetrock (or whatever surface the mold is on), assuming no mold behind it, replace the sheetrock.  

Hot surface ignitors don't mix well with grease.The home was rented with no appliances included, and the lease backs that.