May this mail find you in the best of health and Emaan InshaAllah.
1. Is it permissable in Islam for one to work for a secular bank (where riba is common) as an accountant?
2. If one has a riba based mortgage, what should one do, change to a Islamic Mortgage even if they are not totally 100 Shariah compliant? Or sell the house and live on rental property until one has cash to buy?
1. No, because their purpose is riba-based profit and an accountant aids that haram purpose and shares in its responsibility.
2. See this post.
Hajj Gibril Haddad