Will I inherit my mothers business debt if she has a will?

You will not "inherit" the debt, but any debt in her name will become a debt of her estaate and could affect how much you inherit. Debts are paid before distribution so any debt in her name would reduce the amount you may ultimately inherit. If the debts exceed the assets, any additional debt would be "written off", so you would not have to pay out of your pocket for it.

Attorney Christine James is right in that your inheritance is at risk, but more importantly, holding the business for your brother can potentially prevent your mother from accessing entitlements for long term care which she may need when she gets older. Protecting her well being should be priority one. Part of this planning may be to place the business into a business entity (Corporation or LLC) so that its obligations do not become your mothers. Second, and perhaps more important to her than herself (being a parent), is protecting your brother's benefits. If he is receiving or may receive any needs based benefits, then it is important that your mother's estate plan include a special needs trust designed to hold the business (as well as anything else she wants to pass on to him). She needs to take the time to see an elder law attorney with experience in dealing with disabled adult children. Although your mother should be the client to whom the attorney is committed to protect - this is a perfect opportunity for a family meeting with the attorney to find win-win solutions.