If you are looking to monetize an idle domain, looking to third-party platforms would be a good idea. Many of these platforms such as Nameforest ourselves will create a logo alongside your domain, which will be added to the list of preexisting domains on their sites. This is useful as the demand for your domain will also be greatly increased after it is rented as opposed to a domain that leads to a blank site - thus making it easier for you to find a potential buyer.
Lately I've noticed a lot of questions in Q&A centering on purchasing expired domains. A lot of our members have expressed interest in buying old domains for a variety of prices (some are cheap, some are going for upwards of $50k) and want some advice on what to do with the domains once they've been purchased. I'm no domainer, nor am I an expert in such a business tactic, but I generally recommend one of three different options for an expired domain (and would love to hear more if you've got any).
Content setup: If your domain has potential to attract good search engine traffic, you might want to set up some content to help facilitate that. If this helps your domain do better in the search engine rankings then it’s a big win regardless of whether you choose to flip the domain only or flip the domain with the content as a “website”. The SEO value will be helpful either way.
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.