Well,after searching ...proper care housing of rat(s), the consensus is according to several sites,,wire cages or,,,,AQUARIUMS of sufficient size.(Just as I thought).
Problems with respritory troubles are due (as I mentioned), to dirty fouled bedding which in too small an enviornment =ammonia smell which irritates the rat(s)
Keep the bedding changed and there is absolutely nothing wrong with keeping a rat in 55 gal tank or larger.
Could find no evidnece that rat's need company, and is my view that more than one or two,,will ultimately lead to many many babies .They can breed like hamster's.
Just my two cent's.
Can google proper care, housing, for rat's for ones own,(I did) but much offered is opinion, just like other's who have regurgitated what they have heard.My observation's are from expierience with the creatures.
I am pleased that I have managed to keep the children's pet's alive each summer and according to ASPCA,and Fancy rat,mice,association ,have not done wrong.
Put that in your pipe and pull on it a while.