How can I protect my Dad's property if my mother is admitted into a nursing home?

As others have said, see an attorney. Elder care one is good but with the rental property I'd look for an estate attorney to work with. The rental property - if they are in a community property state - could have it so that mom can never qualify for Medicaid because she has too many assets. Medicaid is for the very poor and the state expects you to full spend down the joint assets to basically 2 K for the NH resident and up to 109K for the still at home "community spouse" in some states.
Personally I think that if they have the $ and assets and ability to pay for their care they should and mom will be able to get to be able to choose where she lives and what the environment is like and she is fortunate to do that. If they live long enough, they will eventually run out of $ unless they are really generationally wealthy.

If it seems your dad is reasonably health and will be living in the community for a while but mom is going into the NH and it's not imminent, then you have some breathing time for make decisions. My gut feeling is that this isn't going to be easy especially if he has issues with relinquishing control.

Start looking for an attorney, But you can do some things to get prepared: do a list of all the properties, have current and maybe last 7 years of assessor value on them; go on-line to the county web site and pay to download the act of sale or other legal for each property; get last 7 years of all taxes; and any info on prior marriages (so they can update their wills). This will make the attorney evaluation be realistic and not be an issue later on if they have to deal with Medicaid. Good luck.

Well, it sounds like you'd be a little short of the 5-year lookback period, doesn't it? Of course, Mom may not need an NH for 3 years. Or she may need it in 6 months. Putting the assets in your name now is a gamble.

I suggest consulting an attorney who specializes in Elder Law. He or she will be able to explain what the penalties would be if Mom needs Medicaid before the 5 years are up, and may also have other suggestions for protecting some assets for Dad.

I sympathize with you. Dad can't live on $500/month and has responsibly arranged another source of income for himself. What will he do if he must give up that source in order for his wife to have proper care?

I think the way Medicaid rules work for a couple just plain sucks. But my opinion and yours isn't going to help your father. Please see a qualified lawyer.

Talk with an elder law attorney. You may want to set up a living trust to protect the house and property but an elder law attorney will help you. They know the laws regarding the elderly since it is so specialized now.