Based on a quick calculation on whattomine, at current difficulty and rates, if you run 15 GTX 1080 Ti's (which are the most powerful and efficient NVidia cards atm IMO), you earn roughly 68$ in profit a day. So you get roughly 2040$ of net profit for 30 days of continuous mining after electricity (~200+$ for fully optimized cards at 65% TDP).
The cards will currently cost you 15000$ MINIMUM as prices skyrocketed. Good luck finding those cards. Same applies to other models like 1070's, but then you need more cards for the same daily return. You still need high efficiency power supplies and motherboards, processors, electrical wiring upgrades, cooling and racks. Depending on how professional you want to run your operation count in another 3-5k$ just for that. Especially the upgrade of your electrical might cost you as your power draw can become an issue for standard fuse boxes. If I had no issue with funding, I would build 3 rigs containing 6x1080 TI's. I would run all of my rigs on Ubuntu or another simple distro specifically for mining.
So I would say for a high-end build - at current pricing - you will at least pay 20k$ for equipment.
I currently would suggest not to invest in equipment as prices are ridiculous. A few months ago you could have build the same rig for 10k...
Just my 2 cents on the topic. I have been mining since May 2017 with 1070 rigs.