Isn't the problem that, while the house may cost $30,000, the land on which it would have to reside will inevitably cost far more than that?
(edited to add I forgot to add the cost of a foundation, in the south the freeze line is like 2 inches, but where I live I believe its 4-5 feet, so you're already spending 90% of the cost of a full basement, may as well finish it off and have a basement, but thats another $10K perhaps for something this small?)
TL;DR - buy/access a "plat book" for each county you're interested in, correlate each lot with a topographic map to identify interesting properties, visit the Assessor's Office to find the owners, write a polite but terse offer letter to the owners who live farthest away - good chance they don't want the property and will part with it fast for a reasonable offer. Yes, takes some work & money, but a whole lot less than list price.