In the documentation for user_relationships_load(), it defines the 'limit' option as:

  *   limit
  *     a string containing SQL stating the limit (ex "10" or "10, 5")

However, passing that string causes the range to be set to "0, 0".

Instead, 'limit' should be an integer, and 'offset' should be passed as a separate integer. The $options parameters is passed to _user_relationships_generate_query() which extract()s the keys as variables, and uses $limit and $offset as separate integers on line 253:

  if (!empty($limit)) {
    $offset = !empty($offset) ? $offset : 0;
    $query->range($offset, $limit);
  }

The correct documentation should be something like:

  *   limit
  *     an integer indicating the maximum number of relationships to return
  *  
  *  offset
  *    an integer used together with limit, indicating the offset for a range of relationships