I agree with Messrs. Shepard and Pittman. If you intend to sell it to your brother, you will need a contract of some sort and a deed to properly transfer the property. If there is a mortgage or other liens on the house, that will need to be addressed as well.
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Good afternoon. You should talk to a local attorney specializing in residential real estate. That person should be able to draft as real estate contract and prepared a deed transferring ownership to your brother. I would advise to go through an attorney so that you can be sure that the house is our of your name and no longer your responsibility. I hope this helps.
First off, I am sorry for your loss, losing a mother is a terrible thing.
Now for the less important stuff, I agree with the advice already given regarding executing a contract and a deed to properly transfer the property, but you seem to be considering your brother's death as a potential short term possibility. In that case, what does his will (if he has one) look like? If he does not have one, the property may pass back to you and all your effort to avoid property taxes may be for naught. I recommend you hire a real estate attorney with experience in estate planning to address this problem.
Also if your brother is disabled, will he be able to afford to buy the house from you? If not, the easiest solution would be for you and your sister to quit claim the property to him. A quit claim is a type of deed that transfers title while making no warranties about the property. In effect, you are saying I am done with this and you have to take it "as-is." However, the problem of him possibly passing the property back to you by passing is there and will still need to be considered.
Best of luck and sorry again for your loss.