This is a loaded question, because the market is very volatile. The startup cost can range from nothing (use existing equipment) to several thousand dollars for a single rig.
For example, with crypto mining being very popular, you will see an increase cost of GPUs, high-lane PCI-e motherboards, and high-wattage Power Supplies. You will also have a much harder time finding them, as not only miners will buy up the stock, but so will the public who have caught wind of the boom in reselling. Not buying high-priced items will help drive down costs.
Here is chart which shows how costs go up parallel to how much equipment is needed:
| Action | One-time Cost | Recurring Cost |
|---|---|---|
| Use your existing desktop computer with a high-end graphics card | n/a | Cost of electricity |
| Buy a new graphics card for your desktop computer | Cost of the card | Cost of electricity |
| Buy a computer and a graphics cards | Cost of the computer + cost of the card | Cost of electricity |
| Build your own multi-GPU computer | Cost of the computer + cost of the cards + cost of the peripherals + cost of the OS | Cost of electricity |
Electricity costs are directly correlated to your personal home. A 6-card setup may use ~1000 watts at the wall. For me, this costs around $90 in electricity per month to run, plus the wear on the cards for 100% duty-cycle 24 hours per day, 365 days per year (if they last that long).
You must also take cooling into consideration. When I first started mining, I got the bright idea to run my first rig in the living room of my house. Overnight, the ambient temperature of my home rose about 30°F . Each card jacked its temperature up to about 75°C . Don’t do that; always place it in a room where you can provide ample cooling and plan your electricity usage for the increased cooling.