You can post your properties on VRBO (or other online vacation rental marketing service) and get a virtual tour as well as listing on Mooncreek studios (which will create your virtual tour, post it on Mooncreek studios online vacation rental service, and give you a link so you can put the link on your VRBO site). These work well for condos or homes.
I think the key to success with online rental services is to:
(1) have really nice visuals that present your property in the best light (Mooncreek studios does excellent work -- look at some of the examples on Kurt's link)
(2) have really good text that shows why people should select your property -- I'm surprised at how many people don't use much text in their listings. Without more detailed information, potential renters can't really tell what they're going to get and it also looks like the property owner isn't that "into" their rental properties or their guests' experiences while there.
(3) take very good care of guests when they use your properties so that they'll come back and tell their friends
(4) actively manage the online listings -- for example with new information, discounts if sales are slower than expected in certain periods or if you have cancellations and have last minute deals
(5) work closely and positively with the rental management company if you work with one so that they know your properties well (and know that they are nice places that are well-kept), know you, know that you want them to take very good care of your guests, and have mutual good-will -- I see my relationship with the rental management company as a partnership in which we are both helping each other succeed (and have enough goodwill to over-ride any bumps along the way given that nothing and no one is always perfect)
I hope this is helpful and I wish your friend the best with rentals!