I highly suggest building a home if you will be using it that frequently. If you wanted it mainly as a several week/month vacation home that produces rental income the rest of the year, there are a ton of nice homes for sale, but since you will be spending so much time there it is "practically" a primary residence, you will probably want different features than are typical in the homes being built to accommodate vacationers.
I am wary of older construction because of potential mold issues and the fact that newer building requirements such as impact windows and doors will help you get lower insurance rates, but newer isn't necessarily better as the construction quality can vary greatly.
Please don't try to do your own electrical work and plumbing as suggested above if you decide to build! That has disaster written all over it!