I would suggest that if you wish to let your house to the council under the RAS scheme the best way to go about it is to let the house yourself to a tenant who is not on RAS but entitled to be. That is some one who has been in receipt of rent allowance for more that 18 months, (you will need to check exact rules more thoroughly).
When you have a suitable tenant in place, they can then apply to the council to go on RAS.
I did this sucessfully and the inspection was fairly cursory, I suspect because the tenant wanted the house, the location suited her.
However RAS is no huge advantage to the landlord. The rent is low and be careful what is meant by guaranteed. In my case the rent is guaranteed, that is the council guarantee to pay the rent due. The contract is for 3 years. However the council can give a months notice at anytime. In practice all I am guaranteed is a months notice.
Having said that I am happy with RAS as I get paid on time every month and the tenant gets some social welfare benefit as well.
Regarding the tax clearance cert you mentioned. I dont believe the council is entitled to ask for this unless the rent is more than €10,000 per annum.