diff --git a/modules/users/default.nix b/modules/users/default.nix
index 477cdd4a..4753f14a 100644
--- a/modules/users/default.nix
+++ b/modules/users/default.nix
@@ -66,12 +66,24 @@ let
           only once the name is registered will the service be considered "ready".
         '';
       };
+      readiness.waitExists = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          path to a directory or file whose existence signals the service's readiness.
+          this is expanded as a shell expression, and may contain variables like `$HOME`, etc.
+        '';
+      };
     };
     config = {
-      readiness.waitCommand = lib.mkIf
-        (config.readiness.waitDbus != null)
-        ''${pkgs.systemdMinimal}/bin/busctl --user status "${config.readiness.waitDbus}" > /dev/null''
-      ;
+      readiness.waitCommand = lib.mkMerge [
+        (lib.mkIf (config.readiness.waitDbus != null)
+          ''${pkgs.systemdMinimal}/bin/busctl --user status "${config.readiness.waitDbus}" > /dev/null''
+        )
+        (lib.mkIf (config.readiness.waitExists != null)
+          ''test -e ${config.readiness.waitExists}''
+        )
+      ];
     };
   });
   userOptions = {