Honestly most of the common stuff asked is all in your hands in the form of statistics...
1)What's the best parking company?
Every domainer has different domains, every parking company has different sales links. So who pays the best and who leads to more sales can all be analyzed by looking at your numbers from an A/B/C/D test.
2)What's the best domain sales page?
Is it your own on your own hosting?
https://themeforest.net/item/domain-broker-2-landing-page-to-sell-domains/12578919
Is it domainmarketpro.com?
Is it efty.com? etc...
Few month test will give ya all the statistics ya need.
3)Will affiliate links perform better than Adsense?
test it
etc....
You'd be surprised how simple modifications color, location, etc... can really change conversion ratios.
Trusting your financial future on someones opinion can be dangerous.
People can give bad advice either from inexperience, affiliate link suggestions so they profit, etc...
Run with what works for you as someones opinion who holds different categories of domains, sells at different price points etc... might not be the best advice for you.
Numbers don't lie, test A/B/C/D, analyze, adjust, profit.