Excellent information Tim. In addition, all of his material possessions that symbolize the modern world, such as his car and the fridge, have all ceased to work before he has paid them off. The great American Dream has been almost achieved but was it worth the effort? Certainly the possessions are not worth the cost: nothing works as it should, nothing grows as it should, and the cost he has paid on behalf of his dream is also too high: his children are failures.
Willie's house is from another time, and almost another world. He remembers the times when he could plant a garden and even goes out to buy some seeds toward the end of the play. But Willie's house is now surrounded by tall buildings (apartments?), and there isn't enough sun for him to grow anything.
Just as Willie's home no longer allows him to grow a garden, so Willie is no longer able to "grow" in his dreams ... and probably hasn't been able to for some time. His belief in the cult of personality, that business is based on friendship and contacts, belongs to another era, just as his garden has long been an impossibility. Sadly, Willie cannot adjust to these changes, but continues to believe in his vision of what the world is like.
There is also irony in the fact that Willie's home is paid for only after he is dead. He spends his whole life working his way out from under the debt, but never really takes possession of his home. His dream is a failure in business; it's also a failure in his home life.
Wow this is absolutely amazing you guys. Both of you did such a fantastic job on this question. I was going to answer it but...you two stole the show! Great job, couldnt have done it better myself.