Not sure if this has been brought up, did some looking in old posts but couldn't find anything but may have overlooked it in my haste. 

Once you purchase your fortifications you're spending on them is done, unless they are attacked. 

Seems reasonable to have a fortification upkeep cost due to some form of degradation. I mean front gates can rust, doors can get weathered and dogs do get old and have to be put down.

Something along the same lines as BG upkeep but for your forts. 

P.S. please don't hate me for this CL's, it's only money. :P

all those things take years 

I suppose if I had to put a number to it maybe 5% or 10% per week of the total cost of fortifications purchased for your HQ

How about Mother Nature taking a toll?

Dislike this idea.  Money is a precious resource that rarely gets spread evenly without another needless expenditure.  It is already difficult enough for A) People to outfit and upkeep themselves, B) For a Godfather/Chairman/Leader to outfit their army and make sure they are all up kept. 

Any standing army of a considerable size spends hundreds of millions every 5 days if it is being done correctly where the CL/Godfathers are paying for the upkeep of their soldiers.  This is in addition to already spending the $350 million to outfit their soldier with Bodyguards, per soldier.  If the status quo has shifted to where soldiers are expected to outfit and upkeep themselves, then I think this is an even worse of an idea.  If fortifications are needing to be upkept and it's of any sort of expense that bill will fall on the 99% at the bottom, not the 1% at the top.

I could be totally wrong and the paradigm has shifted away from CLs/Godfathers paying for the bulk of the soldiers protection, both buying and upkeeping.  I know it's what I usually do but I can't speak on the status quo today.