Domains that are indexed on Google and highly ranked are particularly attractive to traders. Other SEO aspects, such as backlink profiles or the search volume of the keywords in domain names, also play a significant role in calculating thevalue. Design can also positively affect the price of a domain. Short and succinct names that are easy to remember are especially advantageous. Endings are further factors that should be taken into account. Top-level domains (TLDs) such as .com or .org are by far the most sought-after endings.
Here's an old post on search engine roundtable that claims google's policy is to discount previous backlink juice when a domain changes ownership. I'm not convinced whether this is actually true or something Google says to discourage excessive domain buying / 301 redirecting for SEO benefit. The comments above seem to give varying opinions on this matter. Would be great to get to the bottom of that one!
That said, my recommended budget for beginners would be $500+. Using this budget you could buy a bunch of high-potential $10 domain names, expired/dropped domain names or a mix of both. It’s very important to invest only what you can afford to lose and treat this as a side hustle till you get the momentum going. As you gain experience, industry expertise and some sales under your belt, you can then consider slowly growing your business into a full-time gig.