Just get a good domain name, put up a site, get some traffic (and hopefully some sales) than list it on Flippa and make some money. Think about it, if you only paid $10 for a domain name and a little bit for hosting, and then you sold the site for only $200 that would be a nice profit for such a fast and simple sale. Then try and get one of those keywords, exactly, as your web site name. For instance, in the niche for pussy toys let’s imagine I found a great keyword that gets a large amount of monthly searches without too much competition: cheap pussy-cat toys. Than I would wish to use that as my domain. That way my domain name is a highly searched for keyword which will guarantee rather a lot of free, highly targeted, traffic.
If all your advertising efforts are going to be online I wouldn’t worry too much about the extension. I have had similarly good luck using a .com, .net, or .org. All my promotional efforts are with pay per click or article marketing so no one has to type in my website name, they just click a link which is why I don’t think the extensions matter too much. If you’re going to be promoting in such a way that people would have to basically type in the web site name to find your website, it may make more of a difference. The cheap route can work in a pinch but as soon as you are able to afford $10 or so, get your own name.