Very good article and overview explanation. However I would not recommend buying names with bitcoin, ripple, etc in them. Not only will it be oversaturated those names are brands and can / will be trademarked and you can still be hit with a UDRP. Only register generic names like buycrypto.com, buyingcryptocurrency.com, theblockchain.com, etc. There are tons of opportunities and no need to infringe on a brand name.
Selecting a profitable niche is very important when it comes to domain flipping. Having adequate knowledge in searching domain names is critical. It will help you with fishing as well as parking domain names. Carving out a niche for yourself will enable you to seek out prospective buyers actively who would be interested in the domain names you are offering.
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.