How much, if any, should my mother pay me per month to move in?

jeannegibbs is spot on in her advice to you. I will add some clarification.
Charging room and board, if you are to be "above board" (no pun intended) with the IRS may cause an income tax liability to you. Do a search and the appropriate IRS document will come up.
A taxable event may also occur if you are to charge for personal services rendered.
If you intend on being on the up and up then you may want to look at both options and see which will create the smallest liability (probably room and board).
If you will be charging for personal services having a contract as mentioned is essential to avoid problems if Medicaid benefits are ever sought.
Whether or not you declare the transactions, make sure you keep records.

Absolutely take her money. Why should the elderly not be given the dignity of paying their own way if they are able to? (And contributing at least something if they cannot afford to fully cover their own expenses.)

Also, please have a personal care agreement or personal service agreement in place, that spells out what you are doing for her, what you are providing, and what she is paying. (Maybe room and board and services should be two separate documents. I don't know. Research that online.) The reason this is important is so that if she needs to apply for Medicaid down the road, the money she pays to you will not be considered "gifts" that would cause a Medicaid penalty. Also it helps keep things open and above board in case relatives start questioning things.

How do you know what is fair? I don't know of any guidelines. Consider what her monthly income is. Consider what she was paying for housing and food before she moved in. Consider what your extra costs will be, and also that this is going to consume enormous amounts of your time.

My mother (92, dementia and severe arthritis) moved in with my sister and her husband. Mom gets $800/mo in SS. My sister charges her $600/mo. That is about what she was paying for subsidized housing and food. It gives Mother plenty of spending money for her hairdresser and other simple needs. Mother is on Medicaid and cannot accumulate much in the way of saving, and she at the max. She has her funeral preplanned.

So I think that what my sister is charging is fair and reasonable. (Not that she needed my approval!) But what is fair in your situation I can't say. Hopefully this gives you some ideas for how to start thinking about it.

we also have a specific agreement, that he pays towards his upkeep, 550 per month, but then he pays his own personal expenses above that, eg: nappies/over the counter meds/his monthly bus ticket/his amazonand internet shopping bill/ etc do not come out of this amount. his internet purchases are supervised by my husband. his monthly payment to us is toward rent, board, cleaning, laundry, basic hygiene products like shampoos, conditioners, toothpaste, etc,etc, utilities. it doesn't cover the real amount, but if he paid more he would have no spending money for personal use.
we made it very clear on a spreadsheet with an accompanying typed document what he pays for and what it inludes ....not just for him, but also for the siblings who think we are coining it by having him living with us, when the reverse is true. it costs us prob another 300 a month with his growing needs and dependancies, and looks as that is escalating rapidly.

A distinction in what way, teebee? Either way I think it important to keep track to make it clear the money she gives you is not a gift, but for her own benefit. Whether it makes a difference what you call it in terms of taxes, I don't know. I wouldn't think so -- either way it is income to you, but I am not expert. I hope someone with more specific expertise answers you.

sorry, hit the red button too soon! i think it is important that a) they pay their way so there is a value exchange as we all know nobody appreciates a free ride and in fact giving without receiving often gets used, abused and under appreciated, and under valued b) that they feel they are still contributing and doing something meaningful, like paying their way, or small chores like unpackingthe dishwasher, c) it gets documented so that they and you are clear (ish) on some guidelines and parameters for the relationship, and is a firm arrangement before dementia or confusion step in and mix everything up. good luck!

mylife, I am so sorry for the situation you are in. If your mother didn't need care and you moved in because of your own difficulties, then after a period of getting on your feet I think it would be reasonable for her to expect you to pay room and board.

But she does need care. That is the reason you moved in. Could you leave her alone while you go out and work so that you could pay her? Not if she needs 24 hour care. Check out what a live-in caregiver would cost in your area and show the numbers to your mother.

Yes you were very helpful in answering. Thank you.

Or you could take the money, save it, and buy her a gift sometime for fun

Thank you Mr. Robbins, Appreciate it.

I moved in with my mother to assist her after my father died. I share utility and food expenses, but I also have the burden of all housework (I have living space in the basement, she lives upstairs) and all of the laundry and errands. I also do all of the cooking, even on the days that I work. I don't mind helping with groceries, but I feel that the amount of work I do around the home should be in exchange for room and board. I've tried to approach her with this several times but she gets angry and closes the subject. How can I approach her with this?