My first question with something that old and unused, is what is wrong with them, to much for the risk
There is no risk. You should be able to get what you paid for it at any time unless you're desperate for a sale. I see guys on a regular basis that will purchase something minty, take it out and shoot it, don't clean it properly and snivel when they try to sell it off a few months later for a quick profit and it won't sell for what they're asking. Had one fellow get very upset with me on a rifle he had done just that with and tried for a quick flip because his interests had changed.
Once you clean out the grease, shoot them etc they are no longer mint/unissued. They are now USED/unissued specimens. You pay the big dollar for that grease in the rifle and sometimes the wrapping. Take it out of the wrap, clean off the grease and you're throwing money into the garbage can.
When you're buying a collectible of any sort, don't try to make it better or use it an pass it off as unused. Most astute collectors will pick up on that instantly and likely walk away from the vendor because of a non trust issue. I know I will.
Complete, unissued, in the grease with all matching accessories M1935 Brazilian Mausers will fetch $1500 every day. They have been in that range for a couple of years now. Milsurps have had a rapid increase in price over the past five years. Some people feel they have topped and will go sideways for the next five years. Some people feel the top is a long way off. It's a toss up who's right.
IMHO it's sideways from here for the next few years at least. Some of this will depend on upcoming Liberal firearms policies and manipulations by their bureaucrats.
The 1908 Brazilian Mausers are smoother to operate but don't seem to command a higher price.
South American Mausers are very under appreciated. They are the Rodney Dangerfields' of the Mauser collectors market but that is changing. The rifles were mostly made in Germany or Belgium and many have seen a lot of action in hundreds of unknown South American conflicts. Their time is coming. Usually, the South American Mausers are in better condition than the European offerings at this point.
OP, if you are looking for a shooter rather than a collectible, don't purchase either of the rifles you mention. Look for a lesser grade at half or less than half the price with an excellent bore.
South American Mausers in their original chamberings are usually 7.65 Argenine or 7x57 Mauser. Some later models were chambered in 30-06 and 7.62x51 Nato. Very early rifles were chambered in just about any common European offering but are often black powder cartridges.
Do more due diligence than the comments here. Google is your friend.