Not to sound like a downer, because I really appreciate open source mapping, but that's the part where I think the costs, long term, will swing back.
What if you want to offer transit directions from your location to a rental?
Again, sorry if this sounds like I'm poo-poo'ing your effort; that's not my intention. I think there's another side to this story, though.
EDIT: Forgot to mention my own personal white whale. Google's geocoder is far from perfect, but it's the best I've seen. I worked for years with them, and none of the open source geocoders (or expensive ESRI products) could deal with addresses like Google's. Geocoding is like web WYSIWYG editors; they all suck, but some suck less than others. And everyone thinks they can do it better.
I'm a big fan of OpenStreetMap in theory as well, but once Google launched vector maps with really solid offline caching for their Android app it made it a lot harder for me to consider switching. I know OSM will let you cache tiles for offline viewing, but the level of caching you can do with vector data is a whole different level.
OsmAnd nightly build (0.7.0 branch) is GPL'd, with offline vector OSM maps and it's mind-blowing. Navigation works, with voice. There is now a native rendering option on some devices, it's pretty spiffy. It can also record GPX tracks, with optional background service. The vector map of Croatia is 20 MB compressed, with a huge amount of POI data. Daily, an average of 50000 points are added to the map of Croatia. I've actually stopped using Google Maps, OSMAnd is the best map app and it's completely offline.
The netherlands is a different beast when it comes to Geocoding since each postcode only corresponds with around 10 buildings all very close to each other. Most other systems cover larger delivery areas. My complete amateur comment is that you need different algorithms for different countries.
I frequently have to deliver the bad news to bewildered drivers that the federal building they are looking for is in the middle of Seattle, not on a suburban street Kirkland which just happens to have some similar street numbers - they are always using Google maps directions...
Yes, but the data can be pretty bad, and software to access that data could use some improvement. For geocoding, there is only Nominatim which is a major PITA to get setup. I am still trying to get a full planet import and it has been 30 days on an 8 core 16gb machine with 6 drives in RAID10. Without 64gb of ram and some SSD's, it's going to take a month. Additionally, the results can really really suck. For example, zipcodes are often returned as "97006:97015", a range, rather than as a point. On top of that, sometimes you get the range delimited by a semicolon rather than a colon, etc. The price you pay for user inputted data - there's lots of it, but it's not all quality. Still though, better than paying an arm and a leg!
I've been using Streeteasy.com a lot over the past few weeks. Sometimes I get Google.com maps, and sometimes I get the Open ones. I always think that the Google ones look and function much better. I hope the open ones improve, but it's not there yet.