Hi, Bev. I, too, have used VRBO and Homeway with good results in the US and in France (other than in Paris). In Paris, the problem with VRBO, AirBnB, Homeaway and other vacation rental "listing" services is that the City of Paris is cracking down on "illegal" rentals. Basically, this is because there is a housing shortage in Paris and the City looks at vacation rentals as potential long term rentals for local residents. There are rules about how long and how often someone can rent out their own home or other owned property on a short term basis. Problems arise when other residents in a building complain to the city about the comings and goings at vacation rentals. The other issue is that individual owners who rent out their properties probably do not pay taxes to the city for this activity. On occasion visitors to Paris have booked a vacation rental well in advance, paid deposits or in full, only to learn a short time before arrival that the rental is no longer available. The reasons given are things like: it has been sold, there are bugs, plumbing problems, etc. The reality is probably that a neighbor complained and the city shut them down.
The reason why it may be safer to rent from an agency (as opposed to a listing service) is that the agency represents owners or owns the properties themselves, and the legitimate ones pay taxes to the city. The good agencies that get good reviews are very professional, provide greeters upon arrival, are very responsive to inquiries, etc. Some that get good reviews are Vacation in Paris, Paris Best Lodge, and Cobblestone Paris Rentals (I have booked through them twice). The best advice is to do your due diligence, carefully read the reviews, thoroughly review the rental contract and all terms, contact the agency with specific questions, and look elsewhere if there are any red flags. I am most comfortable when I can pay with a credit card or through PayPal, but some agencies, Paris Best Lodge for example, do want cash upon arrival, but maybe flexible about payments.
This is the short answer, I hope it helps explain the situation. Good luck.