Why do you want an old house? IMO old is not intrinsically better than new. Lots of old houses have the character features removed and if they don't the amount of renovation they need often ends up costing almost as much as building especially if there are issues with foundations, wiring etc. Retrofitting energy efficient fittings to an old house costs a great deal more than installing them as you build especially if you build with a solar passive design etc. Most old houses are built with a very different lifestyle in mind than our current lifestyles - ie kitchens tend to be shut away from the rest of the house isolating anyone who is cooking. Bathrooms are smaller and laundries are an afterthought. Making an old house suit modern sensibilities is not an easy undertaking.
Many new houses are comfortable and charming and many old houses are dreary and cheerless.