VAT on rent

If the property in question, be it residental or commercial is financed via a mortgage I don't see such a big difference. Not sure what PG is, but were I a landlord of a commercial unit I don't think my attitude would change regarding possible reduction of rent for reasons outlined earlier.
 
A PG is a Personal Guarantee. If you have signed a PG you are personally liable for the rent and the condition of the building and all other terms in the lease. The mortgage has no bearing on the rent. This is the amount that is owing to a Financial Institution and they really don't care as long as the mortgage is being paid.
 

VAT registration is not obligatory unless you get more than €37.5k for services in the year. But, if you register for VAT, you have to charge VAT, and remit it to Revenue, even if the amount you get is below the €37.5k. The €37.5k is not a floor under which you don't pay VAT if you are registered - it's just a trigger for when you must register. I think that's the confusion here.