I'm just sort of thinking this through as I type , so I wouldn't cast this in stone but..just from random references throughout the books...
Let's see , Dany is 13 at the start of the series, right ? Back in her infancy , the secret marriage pact was made, witnessed by the Sealord , signed by Darry and Oberyn ...Perhaps following this ,Oberyn forms his company of sellswords , and one could speculate that his original intention in this was something along the lines of the Golden company, to provide a support force for Viserys / Dany when they return to Westeros ( but that's a side speculation ).
It seems to me that the Sealord must have been something more than an official witness , since the house with the red door seems more than just a rental. Yes , Doran could have been footing the bill from Dorne , but I don't think he can have been their sole source of support. I think possibly the Sealord was contributing to their support as well .
( I don't really have time to do a search till later , but there's something about the colours of doors of the buildings in Braavos being a sign of who or what institutions they belong to that's sort of niggling at me. We know , of course , about the HoBaW, but I seem to recall other passing references to door colours from Arya's travels in the city . )
However that turns out , the SERVANTS in the house turn V & D out when Darry dies , which makes me think that the house is owned / run by some powerful person / institution . Dany remembers Darry as old , which makes us accept his death as natural , and quite possibly it was , but you would think, either way , Dany and Viserys would still have whatever financial support they may have been recieving from Doran ( and the Sealord , if he was more than a witness )...Darry only signed on their behalf, he was not actually a principal in the agreement.
I'm feeling that when Darry died, the Sealord also died , and his successor didn't want to continue in the agreement . The servants are not mere hirelings , but serve the office of the Sealord.
Another possible vague clue to this ( one that delights me ) is that 13 years after the pact , we have the " first sword to the Sealord of Braavos " , hiring himself out as a fencing master in KL. ( This could open the whole Syrio can of worms..either the first sword
does run, or at least have the good sense to leave where he's no longer wanted..or if you subscribe to the Syrio = FM line of thought, maybe he
didn't run and was killed, or sought an end at the HoBaW ...
He's not immortal 
..but that's incidental to this thread . )
It's Arya who thinks , in ADWD that "
when the Sealord dies , the knives come out "..If the succeeding Sealord is of a different faction , purges could be a common thing , and old though he may have been , Darry's death may have followed the death of the Sealord , and may not have been as natural as we've assumed.
Perhaps with the death of the current Sealord and the installation of a new one , Dany's star may rise in Braavos. Doesn't the Kindly man state, or imply that the Sealord has been dying for some time ? A lot of the FM / Alchemist activity we've seen might just be to be as ready as possible , as informed as possible as to where all factions stand in anticipation of this turnover.
Edited by bemused, 22 June 2012 - 02:29 PM.