Dictionary Word/Pronounceable/Memorable/Brandable: A dictionary word domain name is very valuable. Of course, the more popular and widely used the word is, the better. For example, “marketing.com”, “cars.com” and “hotels.com” are 7-8 figure domain names. Even if a domain name isn’t a dictionary word, being pronounceable and/or memorable and/or brandable are all big pluses that add to its value.

The practice of exploiting misspelled variants of popular websites for personal gain is known as typosquatting. Users who incorrectly enter URLs into a browser’s search bar may be getting more than what they’ve bargained for and end up on a squatted domain. We’ll show you how typosquatters exploit the simple workaday mistakes of internet users and how website operators and their visitors can...

Surely if you purchase a domain (domain1.com) and redirect it to your existing domain (domain2.com) you expect to loose all ranking for domain1.com. If 301's are used then the objective is simply to pass on authority, not dominate the search results with 2 domains. If you want to keep domain2.com in the index then you would take Rebecca's option 2 or 3.

In the past, expired domains were used as part of black hat SEO in order to generate backlink sources quickly and easily, and this practice is still used somewhat today. Getting links in this way is not a recommendable practice. All relevant search engines work nowadays with highly complex ranking algorithms, which can no longer be outsmarted by these link networks.
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.