In Act II, scene 1, what was so controversial about the house mama bought

It is in a white neighbourhood

Explanation:

In "A Raisin in the Sun" we encounter a black family from Chicago. They have just received an insurance payout following the death of their father. The mother of the family, Mama, dreams of owning her own house, and this is what she wants to do with the money. On the other hand, her family has different ideas. Eventually, the mother does buy a house, but this is in a white neighbourhood, making the decision extremely controversial.

it is in a white neghborhood