I totally understand how hard it can be to say 'no'. But I can now see all too clearly how important it is to have an upper limit and to stick to it. Hence I try to keep away from RIN, Preloved etc.
There is something of an addictive aspect to obtaining a new Pet and on here of course we all join in the excitement when an RUer posts about having done so. But as I have said, there has to be a limit. That limit may be 2 for some, 20 for others. As long as the person never lessens the standard of care given to the pets they already have, that it wont be 'squeezing one more in' and that the financial implications are definitely manageable, even if the newbie developed serious and/or chronic health problems, then fine take on another Pet. But I try to hold off the active encouragement to do so to enable the person to take a step back from the situation and really think it through.