I based the 5% on many factors including the small size of the building, the roof being new two years ago and the overall durability of the structure.

Yo Jerry ,,,hope all is well up in "Gods Country"About your project;The easy answer is .when dealing with decomposed,rotten or failing pipe especially "rough cast iron drain pipe" it is best to simply remove and replace the original bad material.You want clean smooth surfaces on your drain lines especially if this is a rental,,it assures proper draining and trouble free service .In this case,Jerry I would take my time and do a thorough analysis and inspection of these original drain lines.I would certainly invite a competent local family owned and operated plumbing company to perform a sewer video camera inspection and make you a dvd showing the condition of the drainlines.If you have cracked cast iron pipe above ground its very likely you have more of it along with cracked 4" red clay drainpipe underground.If this is the case ,you must bite the bullet and have it replaced.Cracked pipe can be saved with epoxy "lining systems" but I'm not crazy about them.Yeah they are OK if done right,but at the end of the day you still have cracked crummy pipe with a liner.I like to dig up ,remove and replace bad drainpipe.Another better alternative is Trenchless Pipe Replacement or "Pipe Bursting" ,,,with this process you break the original cracked pipe out of the way and actually "pull " new PE polyurethane drainpipe using the old pipe as a guide or conduit.Check out the many excellent animated and real video footage  demos of the process on You Tube,,,,,I dont like mixing cast iron with the black ABS plastic drain pipe.I like one or the other.No hub cast iron pipe is much more durable than ABS but really doesnt cost much more.However ABS will work fine if properly installed,that means pipe and fittings are glued properly and horzontal pipe is installed and "hung" at a 1/4" inch per foot grade.You asking me about burying Fernco rubber "boot" fittings underground.I dont like them .Burying a UPC code approved "No Hub Coupling" which is a black neoprene sleeve covered by a pliable stainless steel jacket is fine.Again if its installed properly.Youll need whats called a no hub torque wrench and you tighten these suckers up to 72 inch pounds.Your friendly counterman at the local Plumbing Supply House will show you how they work.But while you there,,,I would make friends with that counterman and at least ask for a referal to a competent local plumber that takes on small projects invite him to look at your job and get an honest opinion of the condition of your drainlines and whats needed to correct things.Then youll know without a doubt whether its a DYI project or a case where your better off hiring a pro,Good luck Jerry and hope this helpsDD in L.A 

Cotton, lead, sugar, etc have risen in price more than gold, but imagine how much lead or sugar or cotton you would have to store to keep a million dollars worth... and transportation, and some of those are not so durable...

I want to create something that is maintenance free and durable. 

What kind of material would you use that is ideal (low cost, durable, etc.)? 

I have purchased unique King head boards for each room and looking for recommendation for King bed frames that are durable?

(durability).What price range is this rental?

They are durable and dont swell like laminate or hardwood from pee or spilled water bowls being left.  

@Paul Ewing Very good point about the durability of prefab pans.The right solution is use deck mud underneath the pan to fill the air space so there will be no flexing.  

If each unit does not have their own specific space I would put the patio, chairs and a table or two smaller tables Maybe an arrangement of colorful adirondike chairs (very durable).