It may be good to ask yourself a different question. Which one of the following paths do you want to take in your life because a decision like this has long term consequences:

Option 1.
Breaking the law. Spending time trying to cheat the system. Being secretive and having people around you being suspicious or worried. Risk losing the money to shady characters, thieves or even fines/retroactive tax charges. Maybe even risk going to jail. Not being able to freely use the money for larger purchases or investments where fiat is needed. Never being able to fully relax, always on the lookout.

If you want this option I don't have any advice for you more than don't do it. Not only will it give you a poor quality of life, it will affect people close to you. Don't do it.

Option 2 (recommended).
Following the law. Spending time on what matters in your life. Being able to do whatever you want with your money. Enjoying the security of societal structures like banks, law enforcement etc. Being able to sleep well at night, not worrying. Being free.

This is the option you want. Just contact a reputable tax advisor, tell him/her about your situation and get advice on how to proceed. Pay taxes and enjoy your life. Also, consider using some of the money to make the world a better place. Be a force of good in the world.

Sure, but that doesn't change the laws of thermodynamics. They need to eject all that heat to the outside and using two small fans to do it is just impossible. They even say one of the fans is used for backup, so one small fan should cover the cooling requirements which is just silly.

Even if they have figured out a way to keep the air separate from the electronics (to avoid filtrating the air) they still need to eject all the heat.

They either don't know what they are doing or they are trying to scam people. They should be able to show the calculations for ejecting the heat, that part is not secret. Or they could even give the specs of the fans and we could calculate it ourselves.

Maybe these issues have been raised earlier (I didn’t read the whole tread):

A project like this has the chicken and egg problem. Sellers won’t sign up unless there is a big market already using the site. Buyers won’t use the site unless there are a lot of sellers. So it’s extremely hard to launch a service like this.

In order for people to use the service it needs to have clear and big benefits. I don’t really see any at all with this service unless you are a trying to sell/buy stolen or illegal goods.

If I understand correctly the listings will not be censored? If so, that’s really unethical and will contribute to creating a brand image of a service used by criminals and perverts. No reputable seller will want to have anything to do with the service and there will be boycott campaigns.

The existing market places today are not really expensive at all and already have the users sellers want. And the users can pay with fiat, which almost all prefer to do.

Just some thoughts.

Actually, the cave/mountain will not be able to absorb all that heat quickly enough. Not even close. You are going to need a big cooling system..

I like your optimism though and wish you good luck with the project.

I find it very surprising that you think that you will somehow be able to remove all that heat with just two relatively small fans. Please post the calculations that show that to be possible.

Also, where are the air filters? You know you need to filter the air, right?

Since I've actually done calculations on air cooling a container filled with miners I can give you a hint: You basically need one whole side of the container filled with air filters and the other side filled with large fans.