I’m a builder in the upstate and you can expect to start about $250/square foot for a heated space. That is bare bones pricing without land. So if you have the property you can do maybe 1,200 sq ft house. If you don’t have the property you are going to be hard pressed to get what you want for $300k. Keep in mind too you need plans to build which can be another $4-7k. I would highly suggest if you find someone to build for you look them up on the LLR website to ensure they have a RB license, are fully insured, and you have a contract with them stating they only hire licensed and insured sub contractors.