Can myself or my brother (has POA) use some of mom's money to build on a room?

I read your profile and earlier posts. You write above: "My brother has POA and everyone in the family agrees that if I could build a room on I would be willing to take care of mom."

And yet in another post you say your mother lived with your for 3 months and it about did you in. Your H is nearly blind from macular degeneration.

You also say you have 4 brothers. Where are they all? You have only mentioned two of them in your posts.

Everyone in the family agrees that YOU would be willing to take care of mom? Well, of course THEY agree...then THEY won't have to do it!

DO. NOT. DO. THIS. And, as others have suggested, see an attorney. You know deep-down that your mother needs to be in a facility, don't you?

You don't want to place mom in a facility, if you did her funds would last a year? Do I understand correctly? That does not sound like enough money for mom to be in a situation to pay for the addition.

What if there were an emergency where mom needed long term care? She doesn't have enough money for even three month at $12,000 a month. So then bro POA needs to apply for Medicaid benefits for long term care. Through the application process it is discovered that mom paid for a home addition less than five years ago. And they also found she had been paying son for her care or rent in his home without a care contract or a lease.

Medicaid will impose a penalty equal to the cost of the addition plus the amount she has been paying for rent plus any money she has paid to son or anyone for her care.

Whenever an elder pays anyone any amount for anything the most important thing is to consult with an attorney to make sure it is done legally and will not impact Medicaid eligibility.

See an attorney before you do anything of any kind with any more of mom's money.

DO not accept advice from anyone on this forum. There are a few that are knowledgeable on laws in their own states but laws are different from state to state. These people may know generally what is required and allowed. But, none of them are experts on the law even in their own states. They are nor attorneys and that is what you need before taking this any further.

GA gave you very good advice on checking with your jurisdiction on setback requirements in your zone district. See if there are zoning maps online, then check your zone district to see what setback requirements are.

Medicaid would not allow this even if to keep a person out of a facility. Its considered an enrichment to the people who own the home. It increases the value of the home. The owners reap the rewards. I added a shower to the half bath in the room Mom used. The cost was 7K. Planned on recouping the cost when Moms house sold. Good thing a thread on the forum was about what we are talking about now. If Moms house had sold while she was on Medicaid, recouping that 7k would have been a no no and she would have been penalized.

And I agree with GA, townships can be very specific about add ons. We had a family that did that here, they wanted a little kitchenette put in the room. Nope. So the contractor agreed to put the pipes in and cover them with sheet rock. After inspection he went in and put in the kitchenette.

Before you go any farther, check with the building department in your community to find out if a potential add-on would be allowed.  You'll need rough dimensions, including how close the additional room would come to the minimum setbacks, which are mandated borders on each side of a property.

If you're not familiar with setbacks, they're established by the community/city/town, and ARE enforced.   It would be frustrating to develop a plan, get legal advice, and learn that there's no room for setback in the area where you plan to add a room.

You might also want to consider heating capacity of your furnace, i.e., would it in its current state provide adequate heat to your mother's new room?   Sometimes add ons can push the limits of the house support mechanisms.

Would you plan to have a bathroom or something that requires water?  Don't forget to factor in the cost and timing of extending water, and certainly electricity, to the potential new room.

Another thought if you do go forward is a door in her room for rapid egress in an emergency, and extension of a sidewalk for emergency responders.

The house my parents bought was previously owned by someone who was a paraplegic.    Water had been extended to the bedroom, a sink installed, and a door plus ramp added to the bedroom.   It was designed for easy access and for emergencies.

There are some good photos of how setbacks work here:

https://www.google.com/search?q=setbacks&tbm=isch&source=iu&ictx=1&fir=C28iAcO3nIR3XM%252CBQjN_rcCDTdzwM%252C_&vet=1&usg=AI4_-kTypJEAXdQ2FcawK8G97rpRi1MDAA&sa=X&ved=2ahUKEwivnrvR_s3tAhXWQc0KHcgXCu4Q_h16BAgaEAE#imgrc=C28iAcO3nIR3XM

The photo on the right hand side is probably the easiest to read. 

Also, heed Alva's advice on potential gifting if your mother pays for the addition.   There's also the issue to consider of who pays the additional property taxes, now and in the future, especially if your mother does go into care outside of your home.  

We have seen problems pop up on Forum for just this reason. An elder agrees to build on to an existing home, or to pay a portion of payment for home, and then requires care and moving to a facility on medicaid, causing problems. The elder's money was spent down on this addition to their child's home; medicaid asks that that amount be returned before they will supply care. And as POA for that person to be building onto their home would be a very dicey situation.
I would not do this without seeking the help of a Lawyer, and without speaking directly to medicaid. We often see OPs swearing up and down that the elder will never need governmental assistance, but sadly it sometimes comes to that, and there are problems.
If your Mother has NO dementia, the fact is that she can build anything she wants to; but building onto your home would be considered gifting, if I am correct. There are many here who know more about this than I do so I am hoping that Cali or Mstrbill or igloo or another comes in with an opinion. And finally guess I would say that you cannot risk doing this and having done it on advice from a Forum; I would check with a Lawyer. That is something that you as POA CAN do with your Mom's agreement, and with her funds.