The market-driven principles of the domain trade mean that a domain is only worth as much as the buyer is willing to pay. It is for this reason that criteria such as market potential and usability play such central roles in determining prices. Values can change at the drop of a hat. The price of a domain that was once of little interest to anyone in years past can skyrocket once, for example, a newly founded company takes interest in that same name.
Your course of action really depends on how much work and effort you can put into the expired domain. If you're barely able to maintain and optimize your current site, you probably want to just 301 redirect the old site (note: see my amended comment above about the link value not likely to be passed). If, however, you're more creative and have some time on your hands, you can try your hand at crafting a microsite. If you really know your stuff and are experienced at making money off various websites, you'd probably do well with the third option.
I don’t think that there is a real way to sell your domain fast, you can put it up for sale, depending on domain name, but if there is a fastest way to sell domain name, it’s certainly - having a good enough name, that someone would want to buy. I don’t like .com domain names, but that’s my opinion, instead I prefer Hacks ( I’m from Serbia, therefore most of word in English, in plural ends up with ‘s’, so every word that ends with letter ‘r’ in plural gives you .RS ) so I think that here we have great Hack domain names which would sell fast. Either way, your contact information should be available in WHOIS , so if you have an interesting domain name, every buyer would like to be able to contact you directly.
Park the domain with a domain parking service. Since you may not have content to put on the site, a parking service puts up a dummy page with ads. When people visit and click on the ads, that's money for you. This method works best with popular keyword domains that get lots of traffic. In most cases, you will not have control over what ads appear on your domains.
In theory, you could technically acquire a domain for $10,000 and be able to sell it for $100,000. You could also acquire a domain for $10 and be able to sell it for $100,000, $10,000… or $100, you get the picture. Because of this, it’s hard to recommend a perfect starting budget because your strategy, experience, and the pace at which you learn will hugely affect your buying and selling decisions.