AC cycling on and on

My fiance and I thought we had really lucked out with our first house! we were really picky, as we were trying to avoid buying a major fixer upper! We still had a small budget we really could not go over, so when we found a new home built in the last few years that was just within our price range, we thought we had won the lottery. The roof was in excellent shape, the plumbing was still sound, and the lake house had begun to settle but presented no major concerns. The only concerns looked minor–window gaskets, door sealing, all the little things we expected in a new home that had been owned by the same family for several years. After our first month in the house, we got our first utility bill–we could not believe how high it was! we hadn’t even noticed the A/C was cycling so much. Come to think of it, the HVAC was never really quiet. We called a HVAC service provider to come out and look over the system, and it did not look good. Though we changed the air filter our first day in the house, there was already gross buildup in the ductwork from the previous owner. Not only is the air duct dirty, but there are important gaps in the system that need to be repaired. Now weI have to spend money for an intensive duct sealing and duct cleaning. So much for buying a new lake house and avoiding major troubles! If we had purchased an older home, we could have purchased a lake house without forced air.