tell them to get some wild/feeder guppies, and send them to guppies.com this is a statement directly from them.
Although guppies will live in water from 55 to 105 degrees, just like you, they prefer something a bit more moderate. The effective range for the successful keeping of guppies is from 72 to 86 degrees, with 78 to 82 degrees being the most commonly accepted."
I have personally raised guppeis and if i want a particular male to live longer then i put him in cooler water, i used to keep white cloud minnows with my special male guppys in a heaterless tank. but once again it all depends on your house temp. also guppies will develop slower in cooler water but faster in warmer or higher temps.
No better yet tell them to consider a different pet, or how about a virtual aquarium. lol
sry it just seem like so many people who start the fish keeping hobby don't realize its not just fish in a bowl. and it also requires work. heck all pets require time and proper care.