The bit about the cars is so like the short story When Life Hands You a Lemming by Thomas A. Easton that it has to be the one. The story is in the collection The Electric Gene Machine.
The cars are engineered from a mixture of cockroach and lobster:
A Roachster was a cross between a lobster and a cockroach. Its cockroach ancestry gave it speed. Its lobster ancestry gave it enough size so a little gene-tinkering had made it grow to about twenty feet long.
The trouble is that the Roachsters tend to run away to sea due to their lobster genes. In the story the protagonist Cal discovers that fishermen are catching the escaped Roachsters and selling them as lobster. Cal pays the fishermen to give the Roasters to him and he sets up a dealership selling them as sports cars:
The sport fishermen bring their catch to me now. I pay twice what the cannery paid, install the necessary controls, glass, upholstery, and other trimmings, and sell them as high-status, high-price vehicles. I don't touch their tendancy to run away at the first opportunity. Sports cars are supposed to be high spirited.
The trouble is that the phrase if you lived here you would be home by now does not appear in the story. Other stories in the collection talk about growing houses from seeds, but not from carrot seeds.
Also the story has never appeared in Asimov's magazine. It was first published in Analog in 1989, so the timing is roughly correct. Could you have mixed up the two magazines?