To be honest ,investing on domain/servers is not really some serious start-up will like to invest on.The first they they will buy is the domain and the servers ,which comes for quite cheap.The main investment part either comes for hiring the programmers or marketing etc.How much is your budget ? Don't invest on the ideas,invest on the product.Make sure the blue print of the model is ready,beta version is ready and the project is not in its very first discussions.Because if the product takes another 6 months to launch ,your investment is of no use as you could have invested the same amount in something else which would have given atleast some returns for the time wasted in 6 months.