Why is housing in Indiana so cheap?

You can check -and should check on any particular location you are interested in. A whole entire state is not good or bad. Even a whole city is not specific enough. Look at a maximum of a 1/4 of a small city. Check crime, school records, employment. Read back newspapers on line for local news that may clue you in. But cheap houses mean there is more supply and less demand for some reason. The place you are moving from could have a more restricted supply or a much larger demand.

Indiana is not a real major state for employment so there are probably lots of rentals available and the more that remain empty the lower the rents asked

Generally speaking, cheap housing is in places where there is little opportunity.

Its mostly supply and demand, partly reduced property taxes, partly reduced building expenses, partly more space zoned for residential development, and partly reduced cost of living.

Supply and demand.

I dont know but you might post your question in travel as well.