There's nothing wrong with this at all. Believe it or not, this is how most people that are on a budget fix their cars. Instead of spending hundreds of dollars on just a few parts, they buy a parts car for only like $500. You're getting a lot more bang for your buck doing that. Not to mention if something happens to your car in the future, you won't have to wait a week for your parts to come. You can just grab them off the other car.
My good friend has a beautiful Nissan 240SX, and he has four other Nissans sitting on his property that are used solely for parts.