That Mark X is a commercial copy of a Mauser 98. Great reliable bolt action in my book, every part of it is milled steel. As long as any damage is cosmetic in nature, it would be a decent rifle. If the rust is more than that, or the bore is not in good shape, then the rifle would be more trouble than it is worth.
I still think these are fine rifles, but if it needs a new barrel (which a gunsmith could change to 30-06 easily enough), then in my area I would keep looking. These older rifles are floating around gun shows and shops, and now and then I see ones in very good condition in the 400 to 500 range. If its below 400 and very good shape, I'd buy one. But unless you want it as working rifle, as-is, doing work on a rifle adds up fast.
My best find in recent years was $550 for a pristine FN Mauser commercial rifle from the 50's, with a $300 nikon scope on it. Super metal work and bluing, and very nice wood, except that it has a very thick glossy finish on the stock, the style back then I guess, but too "showy" looking for me.