One good reason to steer clear of mainland.
If you pay rent for a Sim then you are paying for the prims on that Sim. With exceptions of clauses in the convent, where say, there is a Travel system, or X number of prims need to be free for sailing.
It is very simple you pay for a plot or Sim, Then within a reasonable length of time, you should be given permission to return whatever you want. Unless it is agreed that certain prims remain.
In RL you buy a house, you do not expect the previous owners thing to be in that house when you move in, if they are they as it is your house you remove said items, It is the same with SL.
(For information I help run a 14 Sim Historic Estate, also have full permissions on that Estate.)