$1 domains on an OG TLD is pretty much impossible to find nowdays.
namecheap usually has $1 domains on some of the "newer" tlds which has no real affects on your SEO needs, so that is also always an option. .COM is usually always more "Trusted" in terms of a consumer, but for the SE, it's all more or less the same.
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@Limitlessgojo Don't do that, that's one of the silliest ideas I read in awhile, that is pretty much telling google and every SE, you own every one of them. Don't let people tell you otherwise, but Google enjoys kicking down the weak and even more when they are on the ground already. That means Google enjoys fucking over people who has nothing than fuck over someone who is big in the industry.
Further, always consider your future options too, future sales/flipping will also be hard to manage as you would need to sell off EVERYTHING instead of just 1 of your niches, you will rarely see big micro-niches sites do this tactic as well.
Look at thespruce for example,
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https://www.thespruce.com/ - Main Site
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https://www.thesprucepets.com/ - Pets
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https://www.thespruceeats.com/ - Food
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https://www.thesprucecrafts.com/ - Craft
Also, yes, while google treats each website differently, the main website
HAS some affects on every sublevel domain you use.
I had a .net site then i put a subdomain (blog.name.net) on it, it was a very competitive keyword and a totally different niche & market to the original site and within a week, it was top 5s in alot of the keywords I was targeting generating tens of thousands of views per day.
Then, shortly I migrated it out to it's own fresh domain newly brought, 301ed just the subdomain across to the new .com and it kept nearly ALL it's traffic and it grew even bigger within the next few months.
So, yes, subdomains do inherit some level of authority and juices from your original domains and when migrating it out, you do have a chance to keep all that traffic, even IF it's a brand new domain.
Also,Idgaf what google says, they don't even know a tenth of their own system let alone their every changing algos. WEB2.0 backlinking is mere proof it works else noone will be doing web2.0s...