This feature must be developed based on the xml files that will be uploaded. There is no core solution we can integrate. Only custom and will be a large amount of work.
I will do my best to explain why you may experience bigger problems with this one:
1. each client can have xml with different fields, and you will need to create these fields in admin before the import starts so import can be done. XML will need to have certain fields mandatory (lat, long for the pin, images, featured image, title…)
2 each user must know how to assign the fields from xml to your theme fields names (import can happen if this is done). Imagine some properties have 100 fields and user must do that for all 100. 100 is just a number. Can be even more, depending on the xml;
3.you will need to offer technical support for such clients as this is not for non-technical people
4. you will need to a more powerful hosting to support this kind of import. Imagine some client adds 1000 images or more at one time, and takes the server down because it’s too much to handle.
This can be done with custom work, but it will require a big budget and instead of simplifying, it will make the website harder to use.