I disagree that i think mining for profit is gone or that you can't compete with the big PubCos, you can it's just not really with your bitaxe at home... You need to find an edge, and this means it really depends under what conditions you're mining, if you want to have something stable that you can actually project into the future you should aim for the following:

1. Power as close to (or under) 0.03/kWh as possible to compete with the majors
2. Scale... You need a place that hooked up to either a big transformer if you're on grid AT LEAST 1 MW or a large generator to put at least 300 rigs.
3. Stable voltage... (240V) you're going to blow out your PSU componentes (like MOSFETs) if you you have too much voltage variation.
4. Cooling... if you do air cool make sure you have analyzed your ventilation system in order to evacuate all that heat properly, oversize your airflow by a good margin, you gotta keep em cool!
5. Money... you need a lot of money to compete in mining. Having deep pockets or working with someone or multiple people with funds is key as you try and grow.
6. Try and get newer machines to maximize life cycle (payback is longer, but you'll make more sats in the end with a newer gen rig) and you'll be more insulated in market downturns.

I run a flare gas mining operation with sub $0.04 power and about 30 PH/s, with older rigs... shit's mad hard, mainly because of working in the oil field and generator issues, but mining economics can bite you in the ass real quick. It's a lot harder than it seems on paper, but as a bitcoiner, I also love mining.