I don't know how bad the rust is on the inside, but the damage in the photo is easily repairable. I have rust inside on both my doors & bought the inner lower panel from American Classic Truck, just haven't had time to weld it on.
The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." - John Stuart Mill (1806 - 1873)