Cheap car rentals and summer special discounts

My husband has a friend in California who always likes to come to Michigan for a visit. He was just visiting us last year; he stayed here for at least a couple of weeks. Now we will be expecting him again for sure, only at this time money is tight with him. So, if he ever decides to take a trip to Michigan, he would have to cut corners. He might be able to manage if he can save money on renting a car. He usually rents a car, and I think he can get by since I found a good car rental company that is offering a summer special of up to a 50% discount on Luxury and Convertible car rentals. That will save him enough money to be able to make it to Michigan for a visit. He likes to hang out with my husband and/or spend the holidays with us here, so he would want to come if he can save money. It also reminds me about visiting my sister Nora in Illinois; maybe we can rent a car, too, since our car is not reliable for us to drive a long way. A dollar a day is very cheap, yes, who can beat that? I will have to see about that in case we decide to visit my sister. Last year I was hoping we could come this summer, you know.