I found this website when I searched for rentals in Paris, France and there is a French phone number. However the address of the business seems to be in Ireland, which is fine except that is not disclosed on the website. I couldn't find an address on the website at all. During office hours in France a voicemail answered both phone numbers listed.
Although there is a calendar the most recent copyright is 2015. I could not find information on the owner of the website or any reviews posted by people who rented apartments through that company. The FAQs page refers to the Terms and Conditions page http://www.parisapartmentsplus.com/pages/terms-and-conditions. In that page it says "We partner with Paris based managers who provide and manage the apartments listed on our website on behalf of the apartment owners." I could find no information on the managers.
In that page it also says "This rental agreement may vary between apartment managers and is signed on arrival." Only seeing a rental agreement after I have paid and flown to the destination does not seem a fair way to do business with someone. read more