I know I need a new HVAC system

Last year, my daughter and her soon to be husband bought a house.  It was old and dilapidated, but cheap.  They had recently graduated from college,  found career job, and weren’t making much money yet.  They slowly made some necessary improvements and changes.  This sooner than later project was the old heating and air conditioning unit in the basement.. They both required an obscene amount of energy to work properly, and it didn’t give the heat or air they wanted.  The summer was a constant fight with the heat and humidity because of the air conditioners inefficiency.  The winter often found us scraping ice from the inside of the windows.  I know that if they were to contact a HVAC professional and have the unit serviced or even replaced, it would most likely save a lot of money.  They had been stashing money to be able to afford to hire an HVAC contractor to do the maintenance and eventual upgrades. In the  meantime, the air conditioner was set at near seventy, and ran only when necessary, in hope of reducing the electric bill.  They put on layer upon layer of clothing, lowered the thermostat substantially, and hoped that the gas bill was doable.,  They kept hoping they would have enough money saved to be able to get the work done before the next winter.  From everything I’ve read, a new unit is the only way to insure its energy efficiency and its reliability.  I am anxiously waiting for the day when I can sit in their home with them, in total comfort, and without hearing them worry about breaking the bank.  It would be really wonderful.