Why is Mama so set against opening a liquor store in A Raisin in the Sun?

The answer to this question can be found in Act I scene 1
of this excellent play. When Ruth speaks to Mama about the money she is going to receive
as Walter asked her too, Mama gives two reasons why she is not willing to use the money
which is legally hers to invest in a liquor store. Firstly, she says that the Youngers
are not "business people," and thus they are not going to start being business people
straight away. To invest so much money in something that you have no experience of is
obviously a big deal, and Mama is concerned about this
aspect.

Secondly, however, she is also uncomfortable with
it being a liquor store, and she is clearly unhappy about her money being used to sell
something that she personally doesn't agree with. Note what she says to
Ruth:

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Well--whether they drinks it or not ain't none of
my business. But whether I go into business selling it to 'em is, and I don't want that
on my ledger this late in
life.

Thus we can see that
Mama also disagrees with drink, and she doesn't want to use her money to do something
that she disagrees with.