Ann
PIP is not a means tested benefit so any income or savings that you have will not affect the benefit.
If you are only receiving ESA(CB) then it is also not affected by any rental income.
The missing contributions are nothing to do with the rental income, check with the DWP as they have obviously not informed the Pensions unit that you have been receiving ESA.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems