Custom Field added to Client to display entered content in Invoice

Hello, I have a question, after adding a custom filed to Clients, type: text; input field name - (Service address) containing text - one line address, it must be able to accept more than one entry and record them in the form of dropdown select list.
After that when create a new Invoice, after selecting the customer name, the same way already recorded billing address is displayed in to the invoice template, to be able to display all entrees of the custom field (Service Address), if no input data value exist leave it empty, may be have a placeholder, N/A, if one value exist, just display that value, if more than one value is contained to display as a multi select drop down field and to allow the needed value to be selected and to record and display the selected value in the final - saved invoice as an additional line above the product and price table, that contain the filed name (Service address) and the selected data value

Could you provide with guidance how that could be set?