While buying up a ton of domains seems like a great way to make some extra money, the real world results show that it is very hard to make that process profitable. As with any industry, you will have those "golden moments" when someone you read about made it into a million dollar a year business, all while sitting in the comfort of his own home. That could be true, but he probably consumed a lot of alcohol and lost a lot of hair doing it.
Check DA/PA: The “Domain Authority” and “Page Authority” metrics gained significant popularity over the last few years. They seem to correlate well with a domain’s ability to rank in the search engines and hence, a domain having a high DA/PA will typically have a higher value. This is not to say domains with low DA/PA can’t sell for a lot of money because, at the end of the day, it’s just one factor. However, it’s good to take a look at these as they may tip the scale in favor of or against some buying decisions.
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.