If you want to utilize your technical background, I would suggest creating some kind of service that can be used by potential customers.
I would disagree with this. Do I need a technical background to sell AWS or ElasticSearch? I guess yes, so the same is with Crypto, blockchain services
He is right, if you have a technical background you should rather go for selling your own product rather than reselling stuff which has more to do with marketing.
If you're aiming at reselling stuff you should start by looking where the volume is and how high your chances at getting a better deal than the others are.
For mining plans the market is done for, the only legit ones have so little margins you will really need to fleece your customers to make a profit and at the same time hope nothing gets wrong with your main partner. One of the few that was legit terminated the plans just a week ago:
https://support.viabtc.com/hc/en-us/articles/4402753997721-Announcement-on-the-Termination-of-ViaBTC-cloud-mining-service