Mo. Rev. Stat. § 369.234: Preference given association holding first lien.

An association may:

(1) Make without limitation any advances necessary to protect the security of any loan or the priority of lien thereon which shall stand secured by such first lien irrespective of intervening liens;

(2) If it holds a recorded first lien on the property, make an additional loan or loans not exceeding in the aggregate the amount fixed from time to time by the director of the division of finance, which shall be secured by such first lien, for the improvement, equipment or furnishing of such property; and

(3) Make any further advances or loans for any purpose to the extent authorized by the deed of trust evidencing the first lien on the property.