My condolences on the loss of your mother. According to the internet, there would only be federal tax associated with the sale (capital gains) if the mobile home went up in value after you inherited it (unless mobile homes have shot up in price June to December, I'd guess the capital gain is zero -- if your residence was that mobile home when it was sold, I'd guess the home sale capital gains exemption applies, $250K, even more certain there are zero taxable gains). If you and your brother both inherited half of everything, I (not a tax advisor, of course) would have to say the split would not be a tax event for anybody (just each pay half of the capital gains tax, again probably zero). If officially you inherited it, the IRS may be curious about the half of the proceeds your brother received (considering his tax liability), he may want to consult a tax advisor and he may be interested to have a gift letter from you (this assumes the split isn't ultimately payment for work he did for you, interest you owed on a loan you got from him, etc).
