Our database is the sum of all properties currently on the market that are willing to rent to college students, and that number is small. It is a very competitive, fast-paced market, and that's the reason there is a problem in this space in the first place.
From our experience cold-calling properties, 3 out of 5 rental properties are completely unwilling to rent to college students. Many will just hang up the phone. From the already small number of desirable (i.e. close to campus, not absurdly expensive, etc.) rental properties on the market at any given time, only about 40% are willing to rent to students. But we add new properties to the site daily, so our inventory is constantly cycling.
With regard to our pricing, it's something we came up with last week, and we fully expect it to be increased if our current successes in sales justify it. We have additional monetization strategies in development as well--a $1000 ad is not the be-all end-all of our revenue stream. But hell, at this point we're just excited that someone is willing to pay for this thing we've invested our lives into over the past few months.