As per my understanding about your use-case you want to create journals and its entries in a single form of Lease. So, you can us the fields_for for both of them as below:
<table>
#in a :pm namespace
<%= form_for [:pm, @lease] do |f| %>
<%= f.fields_for :journals do |journal| %>
<%= render "journal_entry_fields" , f: journal %>
<% end %>
<%= link_to_add_fields "+ Add transactions", f, :journals %>
<% end %>
</table>
_journal_entry_fields.html.erb
<fieldset>
<tr>
<td><%= f.text_field :dated %></td>
<td><%= f.text_field :account_name %></td>
<%= f.fields_for :journal_entries do |journal_entry| %>
<td><%= journal_entry.text_field :credit %></td>
<td><%= journal_entry.text_field :notes %></td>
<% end %>
</tr>
</fieldset>
Though you need to initialise the journal entries every time a new record is added dynamically. I can't help you with this right now as I'm not on my PC.