Like ErectMedia said, expired domains, TYPO domains, domains for flipping ... are great investment, if you put some effort and learn alot, there's great ROI.
Real estate is worst biz if you don't own construction company. As buyer, you just put your money on ice, OK, they usually don't drop in value for decade (unlike during this crisis) but you won't earn a sh!t or very little in % and also, there are expences, especially when you rent it.
This post on my blog might give you idea about domain biz, rest of the job is to check news on domainnamewire.com, namepros.com, dnforum.com, ......
http://www.webmasterinter.net/2009/1...ecent-traffic/