Sorry, I've never bought fish I didn't have the proper home for already set up, cycled, and ready for them. I think you will find that is the 'standard' not something unusual.
As for the left/right side thing...I am thinking there was some sort of sarcasm as a 5 gallon tank is so small, I actually did LOL! *SUPERSMIL
Not sure what you want from this forum if you ask advice, then don't follow it?
I wish you and especially your fish good luck and hope you research your next fish purchase and do the right thing for the FISH next time.