The Rusty Krab looks no different than the Krusty Krab, besides the fact it has no "K" in the sign and later on it was painted there by Mr. Krabs, but it possibly looks different from the inside since it is a retirement home.
When The Rusty Krab went bankrupt, Mr. Krabs bought the building. This purchase was made before 1988.
Since Mr. Krabs was very likely not 18 when he bought the Rusty Krab, as evidenced by his naval and pirate careers, the Rusty Krab owned a large Tartar Sauce container that was given to him when he purchased the building.
Eugene H. Krabs - He bought the Bankrupt retirement home.