will ownership of the person whom the property transferred to be protected if the accrerelation invoke
No, not if the entire loan balance can't be paid off. If the borrower can't get the funds to pay off the entire loan - all owners will be at risk of losing the property to a foreclosure action.
i mean can the third party keep the house or 50% ownership
Only if they, along with the other owners, pay off the loan and divert a foreclosure action.
if they invoke the accerelation and the original ownership fail to pay, what happen to the third innocent party
They aren't really "innocent" - they are purposefully trying to obtain ownership of the property indirectly by not getting the loan directly themself because they can't qualify individually.
They would lose the property if they and the original owners couldn't pay off the loan balance - the lender would foreclose.
what is the chance that lender approve such transfer
The chances of them finding out aren't to great. But if there ever would be reason for them to double check on the title to the property for some reason - they would find out immediately. So, although you can do it - you take a risk.
You would be better off buying a property with seller financing. I realize that the number of properties aren't there that you might wish to buy. However, you could buy a property that way, clean up the credit, and potentially refinance down the road.
I am sorry that I don’t have better news, but please understand that I do have an ethical and professional obligation to provide customers with legally correct answers, even when an answer is not favorable to the customer.