jackal

I have seen nothing in either the Airbnb or VRBO (actually now HomeAway) terms of service that require an exclusive right of listing on either site.

IANAL, but the Airbnb and HomeAway terms of service do not strike me as actually engaging in a contract with a property, beyond the general legal principles of a website TOS being a contract. A listing on Airbnb or HomeAway is, from the owner's end, handled much like listing an ad for a rental property on rentals.com or listing an item for sale on eBay or even posting an item on Craigslist. Airbnb or HomeAway do not have any contractual rights on your property; they only effectively serve as venues to deliver you sales leads and then conduct a transaction from those leads.

Airbnb is, however, very strict about any leads that come through their site, and they both actively censor contact information (phone numbers, email addresses, URLs, etc.) and monitor communications for attempts to circumvent their booking system. If a traveler finds a property via Airbnb, Airbnb wants to earn their cut and makes it very difficult to bypass paying them their cut.

HomeAway is less strict. There is limited censorship and (AFAIK) no active monitoring of communications through the HomeAway platform for attempts to bypass the HomeAway booking system. That said, the terms of service require that "[m]embers agree not to encourage or advise a traveler to avoid or circumvent the service fee charged by HomeAway," and HomeAway is moving more towards the Airbnb model (a booking platform, rather than just a listing platform).

Previously, property owners paid a tiered (and in most cases, higher--it's currently $399/year, IIRC) annual subscription fee to list their properties on HomeAway, but owners and guests could work out their own payment arrangements, and many owners did not accept credit cards (preferring to avoid the merchant fees of doing so). Nowadays, HomeAway really pushes their HomeAway Payments service by promising owners that allowing Instant Booking through that service will move properties up to the top of the search results and defaulting new listings to the settings that allow that (and the integration really is quite simple and automated)--and by advising guests that payments through the HomeAway platform will receive their "Book With Confidence Guarantee"--but it is not mandatory. Owners may still take payments by other methods, whether their own credit card processors (many of whom have better rates than the 3% fee HomeAway Payments takes), check, or whatever, but in these cases, HomeAway still asks the guest for a credit card number during booking to pay for the HomeAway service fee.

So, HomeAway Payments is not a mandatory and exclusive payment provider for HomeAway listings, and owners are free to take payment by any other method, as long as the guest pays the HomeAway service fee. There isn't anything fishy or wrong about an owner asking for payment outside the HomeAway payment system--many owners of highly-in-demand properties in areas with few alternatives (and especially older, long-time owners used to the traditional VRBO listing methods) will feel confident they can fill their properties without needing to take payments by credit card (these are also the owners who typically eschew "Instant Booking" or "Book It Now"-type transactions in favor of approving individual booking requests after vetting the prospective renters--horror stories of bad renters are all over the HomeAway forums). It's of course up to guests whether they prefer to book properties that take payments through HomeAway Payments (since the guest does get additional protections that way), but if booking a highly-rated property, I don't think there's any reason to be worried about issues when paying with another method (if the owners were flaky or unscrupulous, you'd see mention of that in the reviews).