What is the ruling on dealing with housing associations that deposit money in banks, and what should someone do who joined one ignorantly and has become specialized in housing through it?

If the work of these associations is to collect money in installments to build a house with specific specifications, while they undertake to provide the materials at their own expense, then this is permissible and falls under the category of istisna' (manufacturing contract). The deposit of the associations' funds in usurious banks does not prohibit dealing with them, but they must cease this disobedience, as Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression."