Development Guidance

[enigmawebdev]

Very inexperienced web developer here. I'm trying to understand the general scope of, process, timeline and cost of hiring an individual or company to build a system very similar to aardvak (http://www.vark.com). I have gotten a number of quotes on this but they vary tremedously in terms of scope, cost and timeline. I'm most interested in the back end system of the aadvark website.
Any guindance you could provide me with would be very helpful. Thanks for your help.